What is the impact of public access on the breeding success of ground-nesting and cliff-nesting birds?

Full text

Showler et al., 2010 Collaboration for
Environmental Evidence
Library
CEE review 05-010
WHAT IS THE IMPACT OF PUBLIC ACCESS ON THE
BREEDING SUCCESS OF GROUND-NESTING AND CLIFF-
NESTING BIRDS?
Systematic Review
SHOWLER, D.A., STEWART, G.B., SUTHERLAND,W.J. & PULLIN, A.S.
Centre for Ecology, Evolution & Conservation - School of Biological Sciences - University of East Anglia -
Norwich - NR4 7TJ - UK
Correspondence: d.showler@uea.ac.uk
Telephone:
Protocol published on website: 5 December 2005 - Draft review published on website: 25 November 2009 – Final review posted
on website: 01 October 2010
Cite as: Showler, D.A., Stewart, G.B., Sutherland,W.J. & Pullin, A.S. 2010. What is the impact of public
access on the breeding success of ground-nesting and cliff-nesting birds? CEE review 05-010 (SR16).
Collaboration for Environmental Evidence: www.environmentalevidence.org/SR16.html.

3
1. SUMMARY
1.1 Background
The Countryside and Rights of Way Act 2000 (CRoW), which came into effect in 2005,
has created a statutory right of access to open country and registered common land in
England and Wales, extending the public's ability to enjoy the countryside by opening up
previously out-of-bounds areas. Scotland has similarly formalised access recently through
the Land Reform (Scotland) Act 2003. However, public access (both in the UK and
elsewhere) may have potentially deleterious impacts on habitats and associated flora and
fauna, including species of conservation concern. Within the CRoW Act there is
provision for the relevant authority to exclude or restrict access for the purpose of
conserving flora, fauna, geological or physiographical features of the land in question.
One particular concern and the focus of this systematic review, is the impact of human
disturbance on breeding success of ground-nesting and cliff-nesting birds. It was
considered that a systematic review would assist in evidence-based decision-making
regarding the restriction of access for conservation purposes.
1.2 Objectives
To assess the impact of public access on foot (including associated activities i.e. dog-
walking, picnicking, birdwatching, cross-country running, climbing, angling, mountain
biking and horse riding) on breeding success of ground-nesting and cliff-nesting birds.
1.3 Search strategy
Relevant studies were identified through searches of the following 12 electronic
databases: Agricola, Copac, Digital Dissertations Online, Directory of Open Access
Journals, English Nature‟s “Wildlink”, Europa, Index to Theses Online (1970-present),
ISI Web of Knowledge, JSTOR, Science Direct, Scirus and Scopus. Searches were
undertaken on conservation and statutory organisation websites: Agricultural
Development and Advisory Service (ADAS); Countryside Council for Wales (CCW);
Department of Agriculture and Rural Development (DARD); Department of
Environment, Food and Rural Affairs (DEFRA); English Nature (EN) (now Natural
England); Joint Nature Conservation Committee (JNCC); National Trust (NT); Royal
Society for the Protection of Birds (RSPB); and Scottish Natural Heritage (SNH).
Bibliographies of traditional literature reviews and articles accepted into the systematic
review at the full text stage were examined for studies that had not yet been identified by
any other means. Subject experts were contacted.

4
1.4 Selection criteria
The criteria which studies had to meet for inclusion into the final stage of the systematic
review were:
1. Subject: breeding ground-nesting and cliff-nesting birds;
2. Intervention: human activities of walking (including dog-walking), picnicking,
birdwatching, crosscountry running, angling, climbing, mountain biking and horse
-riding;
3. Outcome: primary outcomes were changes in breeding abundance/density and
population effects (population size increase or decrease);
4. Type of study: any field/empirical study.
1.5 Main results
The searching of electronic databases and the internet produced 14,717 articles (Table 1).
After duplicates were removed, a total of 4,904 unique articles remained for assessment
at title and abstract stage, of which 173 were potentially relevant and required full text
assessment against the study inclusion criteria. Full text assessment yielded a total of 85
articles that were relevant for inclusion within the systematic review. Of these, 27 had
quantitative data (regarding the impact of public access and associated disturbance on
breeding success of ground-nesting and cliff-nesting birds) suitable for meta-analysis but
only 20 provided comparable data. A total of 42 independent data points presented data
regarding the subject area of which 38 could be used for meta-analysis. Four data points
were dropped due to heterogeneity in the scope of study, lack of comparators and lack of
estimates of variance.
Of the meta-analyses that could be undertaken sample sizes were severely limited,
primarily due to the lack of comparable quantitative data presented in studies. Those
undertaken indicate that hatching success and pre-fledgling survival are both significantly
reduced by human disturbance (although the latter outcome was skewed by findings of
one study and thus must be interpreted accordingly). There is no significant overall
effect on chick weight or fledgling success.
There is significant unexplained heterogeneity between studies and species for all the
outcomes examined. The period in the breeding cycle when disturbance occurs; the type
and intensity of disturbance; increased predation when attending adult birds are driven
from eggs and/or young; the habitat, and degree of habituation to people have all been
suggested as potential reasons for variability in avian response to disturbance. Small
sample sizes confounded attempts to derive quantitative relationships between these
explanatory covariates and effect.

5
Taking into account findings of many other (mostly observational) studies subject to
review but which could not be incorporated into the meta-analysis, there is limited
evidence for reduced hatching and fledging success due to human disturbance on foot
(including with associated pet dogs) for some species.
Narrative synthesis shows that the few studies that have investigated the effects of human
disturbance on breeding densities of ground-nesting bird species, indicate that breeding
density (e.g. of common ringed plover Charadrius hiaticula, Eurasian golden plover
Pluvialis apricaria, dunlin Calidris alpina, European nightjar Caprimulgus europaeus
and woodlark Lullula arborea) is substantially reduced by recreational disturbances.
Such reduced breeding density, or lack of breeding success within otherwise potentially
suitable habitat (the latter as yet unproven), may be the main consequence of human
disturbance.
There is little quantitative evidence to draw any firm conclusions regarding cliff-nesting
species, but those few studies looking at impacts of human disturbance on breeding
success of cliff-nesting birds suggest a negative impact on breeding success.
1.6 Reviewers’ conclusions
Implications for conservation
Evidence from quantitative studies (i.e. that subject to meta-analysis) for the impact of
public access on breeding success is ambiguous (primarily due to small sample sizes).
Qualitative/observational evidence derived from many other studies suggests that human
disturbance through access on foot can be detrimental to the breeding success of ground-
nesting birds at all stages of the breeding cycle from territory establishment to fledging.
There are exceptions however, e.g. several species of penguins (Spheniscidae) and two
species of tern (Sternidae). The design and reporting of the qualitative/observational
studies leaves this evidence highly susceptible to bias.
A small number of mostly observational studies suggest that responses to a walker with a
dog tended to be stronger than a person approaching without one; displacement of
incubating or brooding birds led to increased predation risk from opportunistic predators,
especially larger gulls Larus spp. and corvids Corvus spp.
The level of impact is highly variable between species and dependent upon locality and
the disturbances involved. As such, proposed restrictions on access must take into
account sensitivity and vulnerability to disturbance on a species by species basis, and site
characteristics. There is insufficient evidence to draw any firm conclusions specifically
regarding cliff-nesting species, but that which is available suggests a negative impact of
human disturbance upon breeding success of a small number of species for which studies
have been undertaken.

6
Implications for further research
There is much scope for further investigation into the effects of human disturbance on the
breeding success of ground-nesting and cliff-nesting birds. Although there have been
many studies looking at the effects of disturbance, few have robust quantitative data
regarding impacts on breeding success and populations. Evidence given frequently stems
from ad hoc observations rather than from rigorous, structured field research. A number
of studies simply infer that a detrimental impact is presumed, or evidence presented is
anecdotal. Some lack suitable controls, whilst in others disturbance levels (or treatments)
are not well assessed or are poorly defined. Especially useful would be longer term
studies investigating the consequences of disturbance impacting at the population level,
of which to date very few ecologists have tackled. The role of recreational disturbance in
reducing breeding bird densities (and potential site-scale desertion) could usefully be
further addressed. It is evident that for some species the degree of habituation to people
may be an important factor governing breeding success; this could also therefore be a
topic of further research.
2. BACKGROUND
The Countryside and Rights of Way Act 2000 (CRoW), which came into effect in 2005,
has created a new statutory right of access to open country (mountain, moor, heath, down
and registered common land, including wetlands and coastal areas) in England and
Wales, extending the public's ability to enjoy the countryside by opening up previously
restricted areas (HMSO 2000). Scotland has similarly formalised access recently through
the Land Reform (Scotland) Act 2003, which establishes a statutory right of responsible
access to land and inland waters for outdoor recreation and crossing land (HMSO 2003).
However, public access may have potentially deleterious impacts on habitats and species,
some being of special conservation concern in the UK, including several species of
ground-nesting birds e.g. black grouse Tetrao tetrix (Yalden 1986, Baines & Richardson
2007), western capercaillie Tetrao urogallus (Marshall 2005), common ringed plover
Charadrius hiaticula (Liley 1999, Liley & Sutherland 2007), Eurasian golden plover
Pluvialis apricaria (Yalden & Yalden 1989, 1990), Eurasian stone-curlew Burhinus
oedicnemus (Taylor 2007), European nightjar Caprimulgus europaeus (Liley & Clarke
2002, 2003, Murison 2002, Woodfield & Langston 2004a) and woodlark Lullula arborea
(Mallord 2005). Within the CRoW Act, there is provision for the relevant authority
(Countryside Council for Wales – Wales; Natural England (formerly English Nature) –
England) to exclude or restrict access for the purpose of conserving flora, fauna or
geological or physiographical features of the land in question (HMSO 2000).
Yet, the passage of the CRoW Act highlighted the lack of suitable information to guide bird
conservation measures in response to this increased access (Liley 2002). In order to help bridge
this gap, relevant information on the impact on bird populations of disturbance arising from
human access on foot (including with dogs) was collated in a literature review undertaken by
the RSPB (Woodfield & Langston 2004b). This substantial report highlighted the relative
scarcity of information concerning effects of disturbance specifically upon breeding success
and bird populations, and identified the need for more, scientifically robust, disturbance

7
studies. In light of this and earlier recommendations, around this time a few such research
projects e.g. on woodlark (Mallord 2005) and Eurasian stone-curlew (Taylor 2007), were
undertaken. Subsequently, several UK governmental and non-governmental stakeholder
organisations in consultation with the Centre for Evidence-based Conservation (CEBC)
identified the need for an independent systematic review incorporating information from these
and other relevant studies in order to assist in policy formulation and management guidance. In
addition, representatives from a wide range of UK governmental and non-governmental
organisations recognised the impacts of recreational activities on biodiversity as one of the top
100 questions that needed to be answered in order to formulate evidence-based policy
(Sutherland et al. 2006). With regards birds, of particular concern are the effects of human
disturbance on breeding ground-nesting and cliff-nesting species. This is in part due to the type
of countryside being opened up where many ground- and cliff-nesters typically breed, but also
their apparent vulnerability to disturbance and that species of conservation concern are liable to
be impacted.
This review focuses specifically on the impact of public access on foot and associated activities
(i.e. dog-walking, picnicking, bird-watching, cross-country running, climbing, angling,
mountain -biking and horse riding) on breeding success of ground-nesting and cliff-nesting
birds. As well as disturbance studies within the UK, all those potentially relevant from around
the world, regardless of species, were considered for inclusion into the review. This was
considered appropriate on the basis that: outcomes of studies are potentially applicable to
closely related taxa occupying similar habitats elsewhere; compilation of as much information
as possible was deemed to give the best overall assessment of impacts; incorporating studies on
a global scale gives the review a wider perspective and thus relevance to a broader audience
beyond the UK.
This review is therefore designed to be relevant particularly in relation to decisions about
the application of the access clauses of the CRoW Act, whilst having a wider
international relevance for other practitioners and policy makers regarding management
of areas subject to human disturbance. It is also hoped that it will highlight gaps in
research and assist in the formulation of informative research projects.
3. OBJECTIVES
To systematically collate and synthesise published and unpublished material in order to
assess the impact of public access on foot, including associated activities (i.e. dog-
walking, picnicking, bird-watching, cross-country running, climbing, angling, mountain -
biking and horse riding) on breeding success of ground-nesting and cliff-nesting birds.
4. METHODS
4.1 Question formulation
The RSPB identified the need for an impartial and independent systematic review to be
undertaken to evaluate the impact of public access on breeding success of ground-nesting

8
and cliff-nesting birds and identify any affects at the population level. The specific
question to be addressed was formulated through discussion between the CEBC and UK-
based stakeholder organisations with an interest in the review.
4.2 Search strategy
Relevant studies were identified through computerised searches of the following 12
electronic databases:
ISI Web of Knowledge
Science Direct
Directory of Open Access Journals (DOAJ)
Copac
Scirus
Scopus
Index to Theses Online (1970-present)
Digital Dissertations Online
Agricola
Europa
English Nature‟s “Wildlink”
JSTOR
The search terms used were:
Bird* AND access*
Bird* AND trampling*
Bird* AND recreation*
Bird* AND walk*
Bird* AND disturbance*
Human AND disturbance*
Human AND activity
Publication searches were undertaken on conservation and statutory organisation
websites: Agricultural Development and Advisory Service (ADAS); Countryside Council
for Wales (CCW); Department of Agriculture and Rural Development (DARD);
Department of Environment, Food and Rural Affairs (DEFRA); English Nature (EN);
Joint Nature Conservation Committee (JNCC); National Trust (NT); Royal Society for
the Protection of Birds (RSPB); and Scottish Natural Heritage (SNH). Google searches
for reports for some species and families were also undertaken.
Bibliographies of articles accepted into the systematic review at the full text stage and
traditional literature reviews were searched for studies that had not yet been identified by
any other means. Recognised experts and practitioners were contacted and asked to

9
recommend any additional sources of potentially relevant information. Foreign language
searches were not conducted. However, the search identified studies on a global scale, all
of which were included in the systematic review process.
4.3 Study inclusion criteria
Studies were initially filtered by title and any obviously irrelevant articles were excluded.
Subsequently, the abstracts of the remaining studies were examined with regard to
possible relevance to the systematic review question. Of these articles (n = 173) 54%
were assessed for relevance by a second independent reviewer; agreement on inclusion
between the reviewers was deemed to be “almost perfect” (Cohen‟s Kappa test: K =
0.864). Studies were accepted for viewing at full text if it appeared that they may contain
information pertinent to the review or, if the abstract was ambiguous (or lacking) and
thus did not allow inferences to be drawn about the article content. The criteria which
studies had to meet for inclusion into the final stage of the review were:
1. Subject: breeding ground-nesting and cliff-nesting bird species;
2. Intervention: walking, dog-walking bird-watching, cross-country running,
picnicking, angling, climbing, mountain-biking, horse-riding, versus no access
or access at a lesser intensity;
3. Outcome: the primary outcome was change in abundance of bird species, and
population effects. Secondary outcomes concerned local effects (e.g. breeding
success and displacement from breeding habitat). However, studies were not
rejected on the basis of outcome;
4. Type of study: any empirical/field study with appropriate treatments and
controls were included in the quantitative synthesis. All other relevant studies
were included in a narrative synthesis.
Studies accepted into the review at full text were considered for relevance by two
reviewers. Any disagreement on inclusion was discussed and resolved by consensus.
Studies not included:
This review specifically investigates the impact of human disturbance (and associated pet
dogs Canis lupus familiaris) through access on foot on breeding success of ground-
nesting and cliff-nesting birds, and associated impacts at the population level. Therefore
excluded disturbance studies included:
1. Studies outside the breeding season (e.g. effects of disturbance during migration
or on wintering grounds);
2. Studies looking at flushing and or/alert distances of birds upon approach of a
human and/or dog, unless undertaken in the breeding season and inferences on
breeding success are discussed;
3. Studies looking at disturbance or predation by feral dogs.

10
4.4 Study quality assessment
A single reviewer (DS) considered articles viewed at full text and studies with
appropriate designs (studies presenting quantitative data with comparators and variance
measures or binomial data) were included in quantitative syntheses. Summaries of
methodology (e.g. study design, timescale, outcomes) were tabulated (Appendix 1).
Other studies for which data could not be included in meta-analysis due to lack of data
comparability with others, and observational/anecdotal studies, are narratively
summarised (Appendix 2).
4.5 Data extraction
Where means and variance measures were available, standardised mean effect sizes were
calculated using Hedges d (Deeks et al. 2001). Binary data were used to generate risk
ratio effect size metrics (Cooper & Hedges 1994, Deeks et al. 2001). Multiple effect sizes
were generated from single studies which presented data on more than one species.
Missing variance was imputed using average values in the pre-fledgling survival and
fledgling success analyses. Data extraction was performed by two reviewers (DS and
GS). Reported outcomes are listed in the form of narrative summaries where qualitative
data, quantitative data without comparators, and data regarding outcomes other than
change in population or abundance of the bird species in question are presented
(Appendix 2).
4.6 Data synthesis
The impact of disturbance was explored using meta-analysis and meta-regression
(Cooper & Hedges 1994, Scheiner & Gurevich 2001, Deeks et al. 2001). These analyses
were performed on hatching success, pre-fledging survival, chick weight at fledging and
fledging success. Data were pooled and combined across studies using DerSimonian and
Laird random effects meta-analysis based on standardised mean difference (SMD)
(DerSimonian & Laird 1986, Cooper & Hedges 1994). The random effects model
anticipates that the true effect size differs among studies and the aim of the analysis is to
quantify such variation in the effect parameters; it is therefore appropriate for ecological
questions where the true effect is likely to vary between studies (Gurevitch & Hedges
1999).
Hedge‟s d effect sizes (Deeks et al. 2001) were derived from the treatment and control
means, standard deviations and sample sizes to calculate standardised mean differences.
The standardised mean difference method expresses the size of the treatment effect in
each study relative to the variability observed in that study (Deeks et al. 2001) allowing
combination of the different bird disturbance parameters reported in the primary studies.
Where continuous data were not presented binary data were analysed using risk ratios
combined in a random effects model using the method of DerSimonian & Laird, with the
estimate of heterogeneity being taken from the Mantel-Haenszel model (Deeks et al.

11
2001). The impact of disturbance on hatching success, pre-fledging survival, chick
weight at fledging and fledging success was examined by inspection of forest plots of the
estimated treatment effects from the studies along with their 95% confidence intervals,
and by formal tests of homogeneity undertaken prior to each meta-analysis (Thompson &
Sharp 1999). A forest plot is a graphical display illustrating the relative strength of
treatment effects in multiple quantitative studies addressing the same question (Lalkhen
& McCluskey 2008).
4.7 Taxonomy and names
Scientific bird names follow those of the IOC World Bird Names online database (Gill &
Donsker 2010). Recent taxonomic changes which differ from those of the original studies
are as follows:
Herring gull Larus argentatus (in Hunt 1972) formerly treated as Larus argentatus
smithsonianus is elevated to full species status, American herring gull Larus
smithsonianus;
Snowy plover Charadrius alexandrinus nivosus (in Ruhlen et al. 2003, and Lafferty et al.
(2006) is elevated to full species status, Charadrius nivosus;
Bridled tern Sterna anaethetus (in Gyuris 2004) becomes Onychoprion anaethetus
Vernacular names mostly follow IOC names, exceptions being: common guillemot
(rather than common murre) Uria aalge and Arctic skua (rather than parasitic jaeger)
Stercorarius parasiticus, which are retained as the IOC English names are rarely used in
the UK. Red grouse is retained for Lagopus lagopus scoticus the British race of willow
grouse L. l. lagopus (rather than willow ptarmigan, as this IOC English name will be
unknown to many readers).
5. RESULTS
5.1 Description of studies
Searching was completed in March 2007; 14,716 articles were captured using electronic
database searches and a small number via other sources. 173 articles remained in the
systematic review after the abstract filter stage (Table 2). Much general information
relevant to the review question was present on conservation and statutory organisation
websites but none viewed contained data suitable for meta-analysis.
A total of 173 articles were accepted into the final stages of the systematic review, with
85 remaining after full text filter. Of these 27 had quantitative data suitable for meta-
analysis (these studies are summarised in Appendix 1), however, only comparable

12
information from 20 of these (38 data points) were appropriate for quantitative synthesis.
Only two studies provided quantitative data regarding the impact of human disturbance
on cliff-nesting species.
Table 1. Number of articles included during each of the systematic review filtering
stages.
Systematic review stage
No. of articles
Studies captured using search terms in electronic databases
(including duplicates)
14,717
Studies captured using search terms in electronic databases
(excluding duplicates)
*4,904
Studies remaining after title filter
419
Studies remaining after abstract filter
173
Studies remaining after full text filter
85
Studies used in meta-analysis
20
* approximate figure
5.2 Quantitative synthesis
Data were divided into four broad categories for which there was sufficient data to
perform meta-analysis: hatching success; chick weights; pre-fledgling survival; and
fledging success.
5.2.1 Hatching success
In five of the six studies (American herring gull Larus smithsonianus, Hunt 1972;
common ringed plover, Pienkowski 1984; hooded dotterel Thinornis rubricollis, Dowling
& Weston 1999; and common ringed plover, Liley 1999, Baines & Richardson 2007)
hatching success was greater in less disturbed compared to more disturbed areas.
Conversely, Yalden (1992) found that hatching success was higher in common sandpiper
Actitis hypoleucos territories with more people (71%) than stretches with fewer people
(58%), though the differences are not significant (Table 2). Meta-analysis illustrates
significant heterogeneity between studies/species (Chi-squared 20.59, d.f. = 6, p = 0.003
but overall disturbance significantly reduces hatching success (pooled risk ratio 1.619,
95% CI 1.246 to 2.104, z= 3.61 p <0.001, Figure 1).

13
Risk ratio
.068412 1 14.6173
Study % Weight
Risk ratio
(95% CI)
1.54 (1.39,1.71) Hunt 1972 24.9
2.05 (1.53,2.74) Pienkowski 1984 19.6
0.69 (0.30,1.57) Yalden 1992 7.3
1.28 (0.97,1.70) Dowling & Weston 1999 20.0
2.94 (1.53,5.66) Dowling & Weston 1999 9.9
5.43 (2.02,14.62) Liley 1999 5.5
1.09 (0.65,1.84) Baines & Richardson 2007 12.8
1.62 (1.25,2.10) Overall (95% CI)
Figure 1. Forest plot of hatching success (disturbed compared with control, or less
disturbed areas) effect sizes. Solid boxes represent the effect size of individual studies;
box size is related to sample size; error bars are 95% confidence intervals; the open
diamond is the pooled effect sizes generated using standardized mean difference random
effects meta-analysis. In this case a risk ratio of >1 indicates a decrease in hatching
success. (See Table 2, for species to which each of the studies refers).

14
Table 2. Proportion of nests hatching in more disturbed, compared to less disturbed areas
for four species of ground nesting birds.
Reference
Species
Treatment (or more
disturbance)
Control (or less
disturbance)
Comparison
Number
of nests
%
hatching
Number
of nests
%
hatching
Hunt 1972
American
herring
gull
375
22 (chicks
hatched/
eggs laid)
483
49.5
(chicks
hatched/
eggs laid)
high vs. low disturbance
areas (assessed subjectively
by no. of fireplaces, beer
cans & picnic groups
Pienkowski
1984
Common
ringed
plover
55
1.7
50
50.5
high disturbance (100+
visitors/day) vs. low
disturbance (c.5
visitors/day) area
Yalden
1992
Common
sandpiper
117
71
140
58
busy (>6 people/km/visit)
vs. quiet (<6 people/km/
visit) sections of shoreline
Dowling &
Weston
1999
Hooded
dotterel
41
24
56
41
Nests on beach (more
disturbed) vs. on dunes
(less disturbed)
Dowling &
Weston
1999
Hooded
dotterel
49
0
5
40
where dogs and people
allowed (more disturbed)
vs. where people allowed
but not dogs (less
disturbed)
Liley 1999
Common
ringed
plover
16
68
139
94
survival through
incubation; daily nest
survival rate at highest
human disturbance level
vs. lowest
Baines &
Richardson
2007
Black
grouse
33
46
22
48
no disturbance (low),
vs. twice weekly
disturbance (high) by
walker
1 number of territories
5.2.2 Pre-fledgling survival
Meta-analysis illustrates significant heterogeneity between species/sites (chi-squared
417.84 d.f. 4, p < 0.001). Although overall access exhibits a significant negative impact
on pre-fledgling survival (DL SMD -4.04909, z 2.00, p 0.046, Figure 2), this significant
result is due to a large negative effect found in part of a study on Adelie penguin
Pygoscelis adeliae (Geise 1996). Within this study this finding only applied to one of the
two treatment control pairs reported. It was hypothesised that variation in the duration of
exposure to access was responsible for this variation but time was not significantly
related to effect size (coef 0.287, se 0.401, z 0.71, p 0.475). Variation in pre-fledgling
survival in response to access is therefore unexplained.

15
Standardised Mean diff.
-68.3631 0 68.3631
Study % Weight
Standardised Mean diff.
(95% CI)
-1.35 (-2.03,-0.67) Flemming et al. 1988 22.6
-59.14 (-68.36,-49.91) Geise 1996 10.2
9.15 (8.01,10.30) Geise 1996 22.3
1.19 (-0.01,2.38) Holmes et al. 2006 22.3
-0.03 (-0.33,0.27) Ruhlen et al. 2003 22.7
-4.05 (-8.03,-0.07) Overall (95% CI)
Figure 2. Forest plot of pre-fledgling survival (disturbed compared with control, or
less disturbed areas) effect sizes. Solid boxes represent the effect size of individual
studies; box size is related to sample size; error bars are 95% confidence intervals; the
open diamond is the pooled effect sizes generated using standardized mean difference
random effects meta-analysis. (See Table 3, for species to which each of the studies
refers).

16
Table 3. Pre-fledging survival/productivity in more disturbed, compared to less disturbed
areas for four species of ground nesting birds.
Reference
Species
Treatment (or more
disturbance)
Control (or less
disturbance)
Comparison
N
outcome
N
outcome
Flemming
et al. 1988
Piping
plover
18 nest
attempts
1.2
chicks/
pair
24 nest
attempts
1.8
chicks/
pair
no. of chicks
surviving/nest attempt to
10 days old in high vs.
low disturbance areas
Geise 1996
Adelie
penguin
37 nests
5 nests
46 nests
31 nests
no. of nests with at least
1 chick raised to 2 weeks
old; smaller colony size
Geise 1996
Adelie
penguin
75 nests
62 nests
63 nests
58 nests
no. of nests with at least
1 chick raised to 2 weeks
old; larger colony size
Ruhlen et
al. 2003
Snowy
plover
83
35
83
65
Cumulative percent
chick survival on high
(weekends/holidays vs.
low disturbance
(weekdays) days
Holmes et
al. 2006
Gentoo
penguin
3 colonies
1.43
chicks/
pair
46
colonies
0.9
chicks/
pair
mean breeding success
(chicks reared to crèche
age) on-station (high
human activity, inc.
some vehicular
disturbance) and off-
station (low human
disturbance)
5.2.3 Chick weights
Meta-analysis illustrates significant heterogeneity between species/sites (chi-squared
12.58, d.f. 4, p 0.014); but there is no significant overall effect of disturbance on chick
weights (DL SMD -0.107, z 0.45, p 0.650).
McClung et al. (2004) in a study of the effects of human disturbance on yellow-eyed
penguins Megadyptes antipodes, clearly show a large statistically significant decrease in
chick weight in disturbed sites (Figure 3). Yellow-eyed penguins appear to grow
accustomed only to minimal well-regulated exposure to humans (e.g. people in hides) but
remain timid where presence of unconcealed people is unpredictable at close quarters, as
in this study. Presence of people may have interfered with adults bringing food to chicks,
or caused chicks to move thus proving energetically costly. Whether fledging weight is a
predictor of juvenile survival was investigated using long-term (1981-2000) re-sighting
data. This indicates that survival probability was positively correlated with weight at
fledging.

17
Conversely, Cobley & Shears (1999) in their study of gentoo penguins Pygoscelis papua,
and Yorio and Boersma (1992) in a study of magellanic penguins Spheniscus
magellanicus, show no effect of disturbance. These penguins appeared to be habituated
to human visitation in colonies regularly visited by tourists, with no outward detrimental
effects (based on behavioural observations) apparent. However, some studies show that
some penguin species or individuals within a colony may suffer from chronic
physiological stress (magellanic penguins, Walker at al. 2006, 2008; yellow-eyed
penguins, Ellenberg et al. 2009) due to human visitation, that could have important
effects but which are difficult to detect. Gyuris (2004) showed that bridled tern
Onychoprion anaethetus chick weights were significantly heavier at 12-13 days old at
sites exposed to higher levels of disturbance but by 21-22 days (fledging age) the
difference was not significant. The effect on chick weight was however only significant
in the first season of disturbance treatment but not in the second. An explanation for this
was that chicks may be adversely affected by human approaches but that these affects
may be ameliorated by habituation to human intrusion into nesting colonies. However,
environmental variables may have played a role (food resources were poor in the first
season) and it is also pointed out that there is much variation in species‟ habituation
ability. Between species/ site variation in the meta-analysis was not related to time (coef -
0.169, z -1.38, p 0.166) and therefore does not support amelioration of disturbance effects
by habituation as an explanation of between-study variation.
Standardised Mean diff.
-1.79783 0 1.79783
Study % Weight
Standardised Mean diff.
(95% CI)
-1.13 (-1.80,-0.47) McClung 2004 19.0
0.39 (-0.82,1.61) Cobley 1999 9.8
0.21 (-0.19,0.60) Yorio & Boersma 1992) 25.6
0.04 (-0.49,0.57) Gyuris 2004 22.2
0.04 (-0.45,0.52) Gyuris 2004 23.4
-0.11 (-0.57,0.35) Overall (95% CI)
Figure 3. Forest plot of chick weights (disturbed compared with control, or less disturbed
areas) effect sizes. Solid boxes represent the effect size of individual studies; box size is
related to sample size; error bars are 95% confidence intervals; the open diamond is the

18
pooled effect sizes generated using standardized mean difference random effects meta-
analysis. (See text above, for species to which each of the studies refers).
5.2.4 Fledging success
Meta-analysis illustrates significant heterogeneity between species/sites (chi-squared
2330.94, d.f. 15, p <0.001) but overall access does not have a statistically significant
negative impact on fledgling success (DL SMD -0.211, z= 0.64 p = 0.525, Figure 4). Two
studies illustrate a significant negative effect of human disturbance. Anderson and Keith
(1980) showed that brown pelican Pelicanus occidentalis fledgling output was greatly
reduced in breeding colonies subject to human disturbance (0.26 fledglings/pair)
compared to those with no human visitation (1.33/pair). In a study of common ringed
plovers, Liley (1999), found that in nesting areas with human access (eggs prone to
trampling) of 36 nests, 4.6% of eggs successfully fledged; in contrast on areas of
cordoned off beach (no access) of 17 nests 12.7% of eggs successfully fledged. Of other
studies looking at the effect of disturbance on fledging success of 13 other species, 12
exhibited a (non-significant) detrimental trend of disturbance. Finney et al. (2005) whilst
finding a trend towards reduced golden plover brood survival to fledging in less disturbed
areas (i.e. further away from a busy moorland footpath) found no detectable impact of the
levels of disturbance prevailing at the study site on reproductive performance overall
(Table 4). Heterogeneity between species/ sites was not related to time (coef -0.169, z -
1.38, p 0.166) and therefore remains unexplained.

19
Standardised Mean diff.
-3.32074 0 3.32074
Study
Anderson & Keith 1980
Anderson & Keith 1981
Beale & Monaghan 2004
Beale & Monaghan 2004
Brambilla et al. 2004
Burger et al. 1995
Burger et al. 1995
Dowling & Weston 1999
Fernandez & Azkona 1993
Finney et al. 2005
Flemming et al. 1988
Hunt 1972
Liley 1999
McClung et al. 2004
Yalden 1992
Yorio & Boersma 1992
Overall (95% CI)
Figure 4. Forest plot of fledging success (disturbed compared with control, or less
disturbed areas) effect sizes. Solid boxes represent the effect size of individual
studies; box size is related to sample size; error bars are 95% confidence intervals; the
open diamond is the pooled effect sizes generated using standardized mean difference
random effects meta-analysis (includes studies with average substituted for missing n
or sd). Data combined using random effects meta-analysis, hedges d effect sizes. (See
Table 4, for species to which each of the studies refers).
Table 4. Fledging success in more disturbed compared to less disturbed areas for 15
species of ground nesting birds.
Reference
Species
Treatment (or more
disturbance)
Control (or less
disturbance)
Comparison
N
outcome
N
outcome
Anderson
& Keith
1980
Brown
pelican
2,663
nests
0.26
fledglings/
pair
3,328 nests
1.33
fledglings/
pair
Mean productivity (young/pair
fledged) in 3 breeding seasons of
nests disturbed by human visitors
at egg/small young stage vs.
undisturbed nests
Anderson
& Keith
1980
Heerman‟s
gull
1,281
adults
4.5
young/100
adults
1,421 adults
17.7
young/100
adults
Number of young/100 adults in
sub-colonies subject to heavy vs.
no known human disturbance
Beale &
Monaghan
2004
Black-
legged
kittiwake
40%
increase in
visitor
numbers
c.2%
nesting
success
50%
decrease in
visitor
numbers
c.96%
nesting
success
Overall relationship (modelled)
between human disturbance and
nesting success. (Values for
nesting success are approximate
only as read off figure).

20
Beale &
Monaghan
2004
Common
guillemot
40%
increase in
visitor
numbers
c.36%
nesting
success
50%
decrease in
visitor
numbers
c.87%
nesting
success
Overall relationship (modelled)
between human disturbance and
nesting success. (Values for
nesting success are approximate
only as read off figure).
Brambila et
al. 2004
Peregrine
falcon
2 nests
(climbers
present)
50%
14 nests (no
human
disturbance)
79%
Nesting success (young reared to
fledging) at cliff sites subject to
climber disturbance only (i.e. no
raven Corvus corax present) vs. no
human disturbance
Burger et
al. 1995
Least tern
12
colonies
29%
13 colonies
73%
Percentage of numbers of pairs
raising >0.5 young/pair in more
frequently disturbed colonies vs.
colonies (1983-1990) with few
disturbances
Burger et
al. 1995
Least tern
13
colonies
32%
5 colonies
27%
Percentage of numbers of pairs
raising 0.1-0.5 young/pair in more
frequently disturbed colonies vs.
colonies (1983-1990) with few
disturbances
Dowling &
Weston
1999
Hooded
dotterel
49
clutches
0
fledged/ne
st
40 clutches
0.53
fledged/ne
st
Mean number of fledglings/clutch
at nests on beach with „least
managed conditions‟ (i.e. walkers
and their dogs (on a lead) allowed
at all times vs. „most intensive
management regimes‟ (i.e. no
dogs; Plover Watch; restricted
access)
Fernández
& Azkona
1993
Western
marsh
harrier
6 nesting
pairs
64% (of
25 eggs
laid, 16
chicks)
fledged
5 nesting
pairs
67% (of
24 eggs
laid, 16
chicks)
fledged
Fledging success of disturbed vs.
undisturbed pairs
Finney et
al. 2005
Eurasian
golden
plover
13
20%
13
10%
Brood survival to fledging (derived
from model residuals of survival
nearest (c.100 m) to furthest (1,200
m) from a major upland footpath
Flemming
et al. 1998
Piping
plover
16 nests
0.5
fledglings/
pair
21 nests
1.8
fledglings/
pair
Chicks surviving to fledging/nest
attempt in areas of high vs. low
disturbance (mean of 4 breeding
seasons, 1979-83) doesn‟t appear
correct in forest plot
Hunt 1972
American
herring gull
375 nests
0.288
young
fledged/ne
st
483 nests
0.606
young
fledged/
nest
Number of young fledged/nest at
gull colonies on islands subject to
greater and less frequent visitor
disturbance (mainly picnickers);
measured subjectively on basis of
„number of old fireplaces, beer
cans and picnic groups‟
encountered during visits
Liley 1999
Common
ringed
plover
36 nests
4.55
17 nests
12.64
Mean % of eggs fledged in areas
with human access (eggs prone to
trampling) vs. no access
McClung et
al. 2004
Yellow-eyed
penguin
19 pairs
0.95
14 pairs
0.79
Number of young successfully
fledged/pair in a more disturbed vs.

21
less disturbed area
Yalden
1992
Common
sandpiper
23
territories
65%
12 territories
83%
Proportion of territories
successfully fledging young
Yorio &
Boersma
1992
Magellanic
penguin
36 nests
1.06
54 nests
1.04
Breeding success (chicks
fledged/active nest) in a tourist vs.
non-tourist area
Assessing publication bias
To test for publication bias in the studies related to fledging success we performed
Egger‟s test illustrated by a funnel plot (Figure 5). This suggests no evidence of
publication bias. Other sample sizes were too small to perform this test and the presence
or absence of publication bias is unknown.
1/SE(Effect size)
SMD
-3.20662 1.25228
1.3227
38.3045
Figure 5. Funnel plot of fledging success studies to assess publication bias.

22
5.3 Narrative synthesis
5.3.1 Summaries of studies of human access disturbance on breeding ground-nesting
and cliff-nesting birds
Summarised in Appendix 2 are the findings of relevant disturbance studies inclusive of
and in addition to those included in the meta-analysis. Whilst most are specific to
recreational human access disturbance, some occasional information is drawn from other
sources as useful inferences may be drawn from them. For example, „investigator
disturbance‟ papers (which look at the effects of approaches to nests by researchers,
which involve handling of eggs and/or chicks, and sometimes, adult birds) are not
included in the analysis. Clearly this form of disturbance is very different to the question
being addressed in this review, however, a few examples are summarised where they
usefully highlight what might occur through casual visitation to the general vicinity of
nests, by for example, walkers or birdwatchers.
The problem of disturbance by domestic dogs, an issue of conservation concern within its
own right, is summarised in section 5.3.2. Lekking species, which face a specific and
potential problem arising from human disturbance in the vicinity of lekking grounds at
the onset of the breeding season, are addressed in section 5.3.3.
5.3.2 Domestic dogs and disturbance
There are many studies of the effect of human disturbance on wildlife but few look at
disturbance caused by domestic dogs or try to isolate the effect of dogs from the people
that normally accompany them. One review has been published (Taylor et al. 2005)
which attempted to summarise the effects of pet dog disturbance on wild birds. It
highlights how very few studies there are which examine specifically the effect of dog
disturbance on breeding birds, and that much available evidence is anecdotal. This
present systematic review identified some additional studies that looked at the effect of
approaches of dogs and people on flush distances and „alertness‟ of birds (both within
and outside of the breeding season) but they did not attempt to separate the effect of dogs
from people. An exception is Miller et al. (2001) which looked at human versus dog
disturbance of vesper sparrow Pooecetes gramineus and western meadowlark Sturnella
neglecta, but this study does not quantify the effects on breeding success. The impact on
breeding success is perhaps the main issue of concern for conservationists i.e. whether
dogs can influence the breeding population size that a site may be able to support (Gill et
al. 1996).
There is only sparse evidence that dogs directly impact breeding success from a few field
studies and ad hoc observations, mostly where very small numbers of chicks were
predated by dogs e.g. killdeer Charadrius vociferous (Nol & Brooks 1982); common
ringed plover (Liley 1999); European nightjar (Murison 2002); and snowy plover
Charadrius nivosus (Lafferty et al. 2006). Hockey 1997, also reported that dogs predated
chicks, and also eggs, of African oystercatcher Haematopus moquini.

23
Pienkowski (1984) recorded some losses for common ringed plovers at Lindisfarne,
northeast England. Here dogs were responsible for taking one adult bird and destroying
at least five clutches (with possibly three more taken by a dog, but perhaps attributable to
red fox Vulpes vulpes) out of a total of 172 clutches over two years. Perhaps more
importantly, the effect of disturbance by both people and dogs were thought to benefit
carrion crows Corvus corone, which appeared to use vantage points to look for
incubating plover movements and hence locate nests, when displaced by approaching
people or dogs; corvids were the main predator responsible for 34% of clutches lost.
It has been shown that dogs will visit nests and flush incubating birds off eggs.
Woodfield and Langston (2004a), using nest cameras, recorded 12 flushing events of
sitting European nightjars. One was flushed by a dog once whilst incubating, and again
whilst brooding, but in this case the single young fledged successfully. These and other
studies, such as that of Murison 2002 (also European nightjars), have led to the general
consensus that incubating birds that are flushed may betray the whereabouts of the nest
and leave eggs or young vulnerable to predation. Hence the high predation rates by
opportunistic predators (especially crows and larger gulls) recorded for some ground-
nesting species has been attributed to dog disturbance.
A few studies have looked at the affect of human approaches with or without dogs on
nesting bird behaviour (as opposed to actual breeding success). Lord et al. (2001)
evaluated the affect of deliberate human/dog approaches to New Zealand plover
Charadrius obscurus aquilonius nests. This study provides some of the sparse
experimental evidence that nesting shorebirds perceive dogs as posing more of a threat
than humans walking without a dog. Three different nest approaches (commencing at 200
m and approaching to within 5 m) were undertaken to 15 nests: walking, walking with a
muzzled dog on a lead, and running (to mimic a jogger). Flush distances, time off the
nest and distraction display intensity, were recorded. Of the treatments, walking with a
dog caused most disruption, with incubating birds flushing earlier (mean 94 m) compared
to walking/running (mean 64 m). The attending bird also remained off the nest longer
(4.8 min) when approached with a dog, than without (3.4 min). Distraction display
intensity appeared to be unrelated to approach type. The greater flush distances and
longer time that adult plovers spent off their nests in response to a dog with a person
meant that eggs were uncovered more often and for longer, possibly exposing them to
increased predation risk and thermal stress.
Yalden and Yalden (1990) in their study of breeding Eurasian golden plovers found that
adult birds flushed at consistently greater distances when a walker approached with a
dog, than without a dog. Only 37% allowed an approach to within less than 10 m when a
dog was present, whereas 68% allowed such an approach by a walker with no dog. This
greater sensitivity to dogs than people was considered a cause of concern, as disturbance
was daily and about 300 dogs (60% off leads) were estimated to pass through the area
each breeding season. They attributed the death of three, old golden plover chicks to
dogs, and in a later study at the same locality, of 22 radio-tagged chicks, two appeared to
have been killed by dogs (Finney et al. 2004). From this very small sample, it was
tentatively estimated that there was a 23% chance of a chick being killed by a dog that

24
would otherwise have fledged successfully, and that were dog predation eliminated the
proportion of chicks fledging would rise from 21% to 27%. At this locality dogs are
meant to be leashed, but over the study duration 58% were observed not to be, with 14%
running across the moorland under no control. Other breeding ground-nesters here, such
as dunlin, could also have been impacted.
Hoopes (1993) in a study of piping plovers Charadrius melodus on a Massachusetts
beach (USA) found that average response distance (of birds of all ages, all behaviours)
was 23 m for pedestrians (range 10 m to 60 m), but 46 m for dogs/pets (range 20 m to
100 m). Unleashed dogs may also chase piping plovers (McConnaughey et al. 1990),
destroy nests (Hoopes et al. 1992) and kill chicks (Cairns & McLaren 1980).
Liley (1999) and others have observed that disturbance by dogs and people both invoke
adult common ringed plovers with chicks to perform „broken wing‟ distraction displays.
However, unlike most people who quickly lost interest and walked on, Liley noted that
dogs chase them, and the adult birds at his study site would lead such dogs out of their
territories with this display, often far out onto adjacent tidal mud flats. Although not
quantified, this behaviour is presumably energetically costly and may impact both on
foraging activity of the adults and young (that crouch and hide in response to danger),
and at least one chick was seen to be eaten by a dog.
In Australia, Dowling and Weston (1999) examined whether dog management on
beaches increased reproductive success of hooded dotterel. Hatching success in areas of
differing dog management i.e. no dogs from 09:00-17:00 h (although this was sometimes
ignored by dog owners) versus where dogs were permitted at any time, were compared.
They considered that there was no intrinsic difference in habitat quality which might
otherwise confound the results. Hatching success was significantly higher where there
was dog management (12.2% of clutches hatching) compared to where dogs were
permitted, where none hatched. It is possible that some eggs were crushed or eaten by
dogs (no direct evidence given), and also that by flushing incubating adults opportunistic
predators benefited. Another comparison was made of the average number of chicks that
fledged per clutch in areas designated as dog-free (but people allowed) with areas with
dogs (dogs and people allowed at all times). There were a significantly higher proportion
of chicks fledging in dog-free areas (averaging 0.65/clutch), compared to areas with dogs
where no chicks fledged. At this locality, management implementation and better
enforcement as the study progressed had a positive effect on hooded dotterel breeding
success, with losses attributed to dogs being greatly reduced as a consequence.
No identified studies quantified the effect of dog disturbance on gamebird breeding
success (see also „5.5 Lekking species‟), but the opinions of those with knowledge of
these species is that dogs cause problems. In a questionnaire survey of the effects of
recreational disturbance of western capercaillie, Marshall (2005) found that nearly 75%
of respondents (who had a working knowledge of this species e.g. land managers and
gamekeepers) rated walking with a loose dog as causing the highest level of disturbance,
regardless of time of year. Even when the scenario was that dogs were under control,
overall opinion was similar, highlighting the perceived perception that dogs are a major
cause of concern. Lek and brood rearing times were considered the most critical periods,

25
and loose dogs allowed to range away from tracks were deemed a disturbance threat
throughout the year. Good quality habitat providing cover was thought to some extent, to
mitigate disturbance effects.
Two studies (Picozzi 1971, Hudson 1982) looked at breeding success and density of red
grouse Lagopus lagopus scotticus in relation to human disturbance and associated dogs.
They found that there was no difference in performance of grouse populations on open
access compared with no public access moorlands. But Hudson (1982, in Taylor 2005) in
a simple non-replicated experiment showed that in the grouse breeding season, a dog off-
lead was likely to disturb 7-times more red grouse compared to one on a lead; whether
this affected breeding success was not investigated.
5.3.3 Disturbance at leks
Some lekking species may be especially vulnerable to human disturbance during the
lekking period. The breeding success of black grouse and western capercaillie for
example, is heavily dependent on the males being able to display effectively to females
on traditional leks, this may be compromised by human presence in the vicinity of
lekking grounds. A meta-analysis of mating success in lekking males (Fiske et al. 1998)
highlights that behavioural traits such as male display activity and lek attendance are
positively correlated with male mating success.
Although human disturbance is frequently cited as a factor contributing to population
declines, evidence tends to be anecdotal. For example, in the Peak District of England,
there was a sharp decline, with extirpation of several populations of black grouse between
1975 to1985. Increased human disturbance, as well as severe habitat loss and persecution,
was considered a major contributory factor (Yalden 1986) but no evidence is given.
Likewise, disturbance has been cited as a factor responsible for western capercallie declines
in several European countries e.g. in Switzerland (Mollet et al. 2003) and Spain (Pollo et
al. 2005).
Only one quantitative study was identified that attempted to determine the effect of human
disturbance on foot on breeding success of a lekking species. This study (Baines &
Richardson 2007) experimentally assessed the effects of human disturbance on back grouse
in northern England. In the UK, black grouse are potentially at risk from increased human
recreational disturbance owing to their threatened status and use of habitats to which a
statutory right of human access through the CRoW Act has recently been granted.
However, disturbance treatments were not undertaken in the vicinity of leks and the
disturbance regimes tested (see Appendix 1) had no discernible impact upon breeding
success or grouse populations.
Marshall (2005) undertook a capercaillie recreational disturbance study in Scotland using
the „Delphi technique‟ (a method to evaluate outcomes of actions in scenarios where
absolute answers are not available). This involved collating opinions of those with a good
knowledge of the species via questionnaires. Disturbance of lekking capercaillies was
considered to have potentially major consequences, leading to failure of females to mate

26
and thus breeding opportunities being lost, possibly for the whole season; the brood rearing
period was also considered critical. Loose dogs allowed to stray from tracks were
considered a prime disturbance threat (see „5.4.Domestic dogs and disturbance‟). In recent
years, increased public interest in finding leks to view displays was considered an
additional threat to the dwindling Scottish capercaillie population. In response, protection
afforded to capercaillie was increased by listing it on Schedule 1 of the Wildlife and
Countryside Act (UK), which makes it an offence to intentionally or recklessly disturb
lekking grounds. Summers et al. (2004) also found that capercaillie in Scotland avoided
woodland alongside trails (1 ha/46 m to 1 ha/82 m of track) that were used by people and
their dogs, and suggest that the removal or closure of tracks might increase the extent of
woodland available to capercaillie through reduction of disturbance.
Baydack and Hein (1987) found marked intersexual differences in the response to
disturbance of sharp-tailed grouse Tympanuchus phasianellus at leks in Manitoba,
Canada. Male grouse continued to display despite test disturbances (i.e. parked vehicles,
exploders, scarecrows, taped voices, radio noise and unleashed dogs) in the lek vicinity.
They were only displaced upon the approach of a person but even then generally
remained within 400 m of the lek, returning quickly (usually within 5 min) upon
cessation of disturbance. Females however, were never observed at leks during these
disturbances. The authors therefore suggest that onset of breeding might be delayed and
mating opportunities lost at heavily disturbed leks. Male sage grouse Centrocercus
urophasianus (another North American species) were noted to be much more prone to
disturbance. When flushed by human presence most did not return for 20-30 min, whilst
some wary individuals did not reappear at the lek until the following day. Sage grouse are
declining throughout their range and in several management plans, supervision of public
access for viewing leks is recommended (e.g. Connelly et al. 2000). Joslin and Youmans
(1999), based on field observations, advocate prohibiting recreational activities within 2.4
km (1.5 miles) of leks.
Kålås et al. (1995) undertook a study of great snipe Gallinago media on Dovrefjell,
Norway. Flushing experiments were made at two leks in 1990, males being flushed
during three periods from the end of May to the beginning of July. One observer flushed
the male snipe at midnight (just before the females usually arrived) by walking from a
hide across the lek and back again (about 15 sec duration), where upon all birds left the
lekking ground. The time each male took to return was recorded. They did not become
habituated to flushing (i.e. the average time spent hiding did not change significantly).
Although this study focussed on mating probability in relation to disturbance and risk
taking, Frid and Dill (2002) referring to this study, state, purely on conjecture, that an
ecotourist disrupting a lek and remaining to take photos would force lek members to hide
longer thus precluding matings, inferring that this is therefore a problem for the species.
Such events might occur, but one of the authors of the Norwegian study considers human
disturbance at great snipe leks not to be a problem in Scandinavia (Stein A.Saether
pers.com. 2006). The „International Action Plan for the Conservation of the Great Snipe‟
(Anon. 2004) states that recreational activities (e.g. tourism and fishing) may interfere
with lekking birds and disturb breeding, and that human activities in breeding areas can
facilitate the discovery of nests by predators, but no evidence is presented.

27
6. DISCUSSION
6.1 Evidence of impacts of human disturbance
This review has collated evidence from studies worldwide which have investigated the
impact of human disturbance on foot (including associated pet dogs) on breeding ground-
nesting and cliff-nesting birds, with most information coming from research conducted in
Western Europe, North America, Australasia and South Africa. The results of the meta-
analyses indicate that the bulk of the quantitative evidence relating to pre-fledging
survival and chick weights suggest no effects of human disturbance, whilst the effects for
fledging success are small and ambiguous. Evidence for hatching success is more
indicative of a problem (but based on a small sample size). Most studies examined, both
quantitative and qualitative/observational, point to human disturbance being detrimental
to breeding success of a variety of ground-nesting species (including eider duck
Somateria mollissima, brown pelican, adelie penguin, four gamebirds, 13 species of
wader, three species of gulls, European nightjar, and five species of passerine). However,
both the generally low quality of study designs and the anecdotal nature of many reports
means that this evidence is highly susceptible to bias.
Human disturbance has been reported to have potentially detrimental impacts throughout
the breeding cycle. There are some observations indicating that at the onset of breeding
activity, displaying birds may be disrupted e.g. in the vicinity of leks, and territory
establishment and nest placement may be influenced by the presence of people (with or
without accompanying dogs). As with many studies looking at the effects of human
access disturbance on ground-nesting birds, a difficulty of those looking at the associated
problem of disturbance caused by dogs is that the measures of disturbance differ widely
(Taylor et al. 2005). This therefore makes comparisons between studies tricky and
drawing conclusions from and making practical use of them to draw up management
plans, accordingly difficult. Despite this, available evidence (albeit frequently based on
ad hoc observations and therefore probably inadequate to draw any firm conclusions)
suggests that pet dogs impact on breeding ground-nesting birds, either directly through
predation of eggs, young and very occasionally adult birds, or perhaps more seriously
displacement of incubating or brooding adults leading to predation opportunities for
opportunistic predators.
6.2 Reasons for variations in impact
Possible reasons for variation of impact of human access disturbance on breeding success
of the ground nesting bird species for which studies have been undertaken are many.
Taking into account all relevant studies (regardless of whether subject to meta-analysis or
not) indicates that the scale of impact is highly variable between species, occasionally
within species at differing sites, and dependant upon many factors, but primarily:
i) the period in the breeding cycle when disturbance occurs (i.e. from initial
adult territory establishment and settlement, through the incubation and chick-
rearing phases, to fledging of young); there tended to be greater vulnerability

28
to disturbance during the incubation period. Eggs of non-colonial beach-
nesting species were especially vulnerable to trampling in areas of high
human visitation. When adults were displaced by approaching people or dogs,
eggs were sometimes prone to predation and perhaps also thermal stress
(although there was no absolute evidence for the latter, this is a reasonable
assumption). In some cases were colonial birds were involved, e.g. brown
pelican and gull colonies, the mayhem that ensued following disturbances led
to the birds themselves causing losses either through accidental trampling of
eggs or young, or mortality of young straying from the nest territory by
neighbouring pairs.
ii) the type and intensity of disturbance; this study looked specifically at human
access on foot and associated activities (i.e. walking, dog-walking, bird-
watching, cross-country running, picnicking, angling, climbing, mountain -
biking, horseriding), versus no access or access at a lesser intensity. However,
given the nature of the issue, disturbance levels are inherently difficult to
qualify and quantify.
iii) the presence of opportunistic predators that can take advantage when
attending adult birds are driven from eggs and/or young due to disturbance; in
several studies, especially of waders (shorebirds) but also other taxa, it
appeared that predation opportunities were enhanced by disturbance (both by
people and/or dogs). Upon approach, adult birds were displaced, and predators
(mainly corvids and gulls) in the vicinity were able to locate eggs by
observing the movements of the fleeing adults.
iv) degree of habituation to people; in breeding areas regularly visited e.g. by
ornithologists, researchers or ecotourists, some birds including several
penguin and tern species, appeared habituated to a greater or lesser degree to
regular (controlled) human visitation. In comparison, those same species
exposed to less regular disturbance exhibited higher responses upon
approaches manifested by reduced breeding success and/or behaviour
indicative of alarm or threat, e.g. distraction displays, fleeing the nest or
reduced provisioning of the young.
6.3 Methodological limitations
There are several methodological limitations that need to be considered including:
limitations of the quality of original research, extraction of data and publication bias.
The original research included in the review is of variable quality, with some of the
currently available studies being of inadequate duration and data are sometimes difficult
to interpret. Levels of impact on breeding success are difficult to compare in many cases
as methods are highly variable between studies. The small sample sizes and large number

29
of ecological and methodological study characteristics severely restricted the potential to
explore variation across species, sites and studies.
Meta-analyses are based on small sample sizes and there is significant heterogeneity –
thus care needs to be taken when interpreting pooled effects. Studies are difficult to
compare because the intensity of disturbance is variable and outcomes are measured in
different ways. Sample sizes are too small for individual studies to be significant given
the magnitude of effect suggesting that bigger sample sizes are needed in future
disturbance work. Sample sizes are too small to assess impact of publication bias, except
for fledgling success, so the potential for bias is unknown.
Data extraction introduces bias where variance is imputed, particularly if the variance is
calculated from summary statistics. This method is defensible provided the bias does not
overweight the study, but the combination of large numbers of studies with imputed
variances remains problematic for both pre-fledgling survival and fledgling success.
Sample sizes were too small to explore this using sensitivity analysis.
Although steps were taken to minimize publication bias by searching grey literature, it is
possible that some studies were not identified despite efforts to do so. In a very few cases
where existence of a report or research project was known about but could not be located,
or in order to try and obtain data, authors were contacted by e-mail. Reponses for
requests for data met with low success.
7. REVIEWERS CONCLUSIONS
7.1 Implications for conservation
The evidence base derived from experimental studies on the impact of disturbance on the
breeding success of ground- and cliff-nesting birds is weak. This is primarily due to the
limited amount of comparable quantitative data between studies amenable to meta-
analysis. Thus, based solely on the outcomes of the quantitative syntheses of higher
quality studies, the significance of disturbance is unclear. Qualitative and
observational/anecdotal evidence on the impact of human disturbance on foot (and
associated activities which were addressed in the available literature i.e. dogs, picnicking,
angling, climbing and ecotourism) upon ground-nesting and cliff-nesting birds suggests
that in the great majority of reported cases, disturbance has a negative effect on breeding
success. But level of bias in reporting is unknown. Evidence for habituation to
disturbance is mixed; it has been shown for several bird species that they will become
habituated to human presence (e.g. Lord et al. 2001, Ikuta & Blumstein 2003) but with
many species exhibiting increased sensitivity to higher disturbance levels. Of those very
few studies looking at affects of disturbance at the population level (e.g. Liley 1999,
Mallord 2005), human disturbance constrained population sizes. Such studies indicate
that breeding density of some species (e.g. of common ringed plover Charadrius
hiaticula, Eurasian golden plover Pluvialis apricaria, dunlin Calidris alpina, European
nightjar Caprimulgus europaeus and woodlark Lullula arborea) is substantially reduced

30
by the occurrence of recreational disturbances. Such reduced breeding density, or even
abandonment of otherwise suitable habitat, may be a major, or the main consequence of
human disturbance.
Given the variable outcomes of the results of studies, it is apparent that for most species
in most situations, management options to regulate human visitation in the vicinity of
nesting areas should be guided by the sensitivity of the species affected, the form of
disturbance, and predicted disturbance intensity. Given this, however, some
precautionary interventions, e.g. fencing off of nesting areas on beaches during the
breeding season, restricting unregulated access to lekking grounds, ensuring walkers
adhere to designated paths, and regulations to ensure dogs are leashed in sensitive areas,
are broadly applicable, and pertinent for encouraging territory establishment and nesting,
or maintaining or enhancing breeding success.
7.2 Implications for research
Only six studies (Flemming et al 1998, Yalden & Pearce-Higgins 1997, Liley 1999,
Finney et al. 2005, Mallord 2005 and Taylor 2007) vigorously address the impact of
human disturbance on ground-nesting birds at the population level. Many other studies
have looked at impacts of disturbance on breeding success and displacement to varying
degrees. Some are peripheral investigations undertaken in conjunction with other
research, often conducted only over part of a breeding season, or one or two breeding
seasons. More longer-term studies could therefore be usefully undertaken, both looking at
the impact of human disturbance on breeding success (reduced breeding densities or site
abandonment) and exploring viable management options to mitigate impacts.
There are few studies that look at the effect of human disturbance on cliff-nesting birds.
A number looked at location of nest sites in relation to surrogates for human disturbance,
such as proximity of human settlements and roads, but samples sizes are often very small
and results ambiguous as confounded by other factors. Where colonial nesting species are
concerned, future studies should strive to include true replication of treatments whenever
possible.
Habituation to human disturbance is another area where further investigation is
warranted. Other than a few specific studies of several species of penguin, conclusions
drawn are often somewhat anecdotal due to confounding environmental factors, or
observations (with no structured experimental design) being made during the course of
other studies. Studies by Cobley & Shears (1999; gentoo penguins) and Yorio and
Boersma (1992; Magellanic penguins), suggest no detrimental effect of disturbance
(based on behavioural observations and reproductive parameters) and that these penguins
appear habituated to human visitation in colonies regularly visited by tourists. However,
Walker at al. (2006, 2008) and Ellenberg et al. (2009) show that some penguin species or
individuals within a colony may suffer from physiological stress due to human visitation,
that could have important effects that are difficult to detect in the typically short-term
studies conducted. McClung et al. (2004) showed that yellow-eyed penguins never

31
became particularly habituated to human visitation and that chicks had a significantly
lower weight in a disturbed compared to undisturbed site; this is one of the very few long
term studies (using a 20 year data set) attempting to assess whether fledging weight is a
predictor of juvenile survival; survival probability was positively correlated with weight
at fledging. More and longer-term studies addressing these issues would be pertinent.
Domestic dogs clearly pose a different form of threat to ground-nesting birds than people,
and although dogs do unequivocally cause problems for some ground-nesting birds, to
date most evidence for this comes from ad hoc observations or is anecdotal. Very rarely
has an attempt been made to isolate the effect of dogs from the people that normally
accompany them. Thus studies that quantify the impact of dog-induced disturbance on
breeding success could usefully be undertaken.
8. ACKNOWLEDGEMENTS
We thank all the stakeholder organisations and individuals for their support and
contributions throughout the systematic review process, especially Dr. Peter Robertson
for assistance in formulating the original review question; also all researchers who
provided copies of their papers, data and other information for use in this review, and
especially Dr. Durwyn Liley and Dr. John Mallord for additional comments, discussion
and assistance in providing reference material. This review was funded by a UK Natural
Environment Research Council grant to ASP and WJS. Thank you also for useful
comments from two anonymous referees.
9. REFERENCES
Adams, N.J., Kerley, G.I.H. & Watson, J.J. 1999. Disturbance of incubating African black
oystercatchers: is heating of exposed eggs a problem? Ostrich 70: 225-228.
Ammon, E.M. 1995. Reproductive strategies and factors determining nest success in subalpine
ground-nesting passerines. PhD thesis, University of Colorado, Boulder, USA.
Anderson, D.W. & Keith, J.O. 1980. The human influence on seabird nesting success:
conservation implications. Biological Conservation 18: 65-80.
Anon. 1996. Piping Plover Recovery Plan. US Fish and Wildlife Service, USA.
Anon. 2004. International Single Species Action Plan for the Conservation of the great snipe
Gallinago media. AEWA Technical series no.5. UNEP/AEWA.
Baydack, R.K. & Hein, D.A. .1987. Tolerance of sharp-tailed grouse to lek disturbance. Wildlife
Society Bulletin 15: 535-539.
Baines, D. & Richardson, M. 2007. An experimental assessment of the potential effects of human
disturbance on black grouse Tetrao tetrix in the North Pennines, England. Ibis 149: 56-64 Suppl.

32
Bayfield, N.G., Watson, A. & Miller, G.R. 1988. Assessing and managing the effects of
recreational use on British hills, pp.399-414, in: Usher, M.B. &. Thompson, D.B.A. (eds.)
Ecological change in the uplands. Blackwell Scientific Publications, Oxford, UK.
Beale, C.M. & Monaghan, P. 2004. Human disturbance: people as predation-free predators?
Journal of Applied Ecology 41: 335-343.
Bêty, J. & Gauthier, G. 2001. Effects of nest visits on predator activity and predation rate in a
greater snow goose colony. Journal of Field Ornithology 72: 573-586.
Bolduc, F. & Guillemette, M. 2003. Human disturbance and nesting success of common eiders:
interaction between visitors and gulls. Biological Conservation 110: 77-83.
Bowles, M.L., Diersing, V.E., Ebinger, J.E. & Scultz, H.C. (eds.) 1981. Endangered and
threatened vertebrate animals and vascular plants of Illinois. Illinois Department of
Conservation, USA.
Brambilla, M., Rubolini, D. & Guidali, F. 2004. Rock climbing and raven Corvus corax
occurrence depress breeding success of cliff-nesting peregrines Falco peregrinus. Ardeola 51:
425-430.
Burger, J. 1981. The effect of human activity on birds at a coastal bay. Biological Conservation
21: 231-241.
Burger, J., Gochfeld, M. & Niles, L.J. 1995. Ecotourism and birds in coastal New Jersey:
contrasting responses of birds, tourists, and managers. Environmental Conservation 22: 56-65.
Cairns,W.E. 1982. Biology and behaviour of breeding piping plovers. Wilson Bulletin 94: 531-
545.
Cairns, W.E. & McLaren, I.A. 1980. Status of the piping plover on the east coast of North
America. American Birds 34: 206-208.
Connelly, J.W., Schroeder, M.A., Sands, A.R. & Braun, C.E. 2000. Guidelines to manage sage
grouse populations and their habitats. Wildlife Society Bulletin 28: 967-985.
Ceballos, O. & Donázar, J.A. 1989. Factors influencing the breeding density and nest-site
selection of the Egyptian vulture (Neophron percnopterus). Journal of Ornithology 130: 353-359.
Cobley, N.D. & Shears J.R. 1999. Breeding performance of gentoo penguins (Pygoscelis papua)
at a colony exposed to high levels of human disturbance. Polar Biology 21: 355-360.
Cooper, H. & Hedges, L.V. (eds.) 1994. The handbook of research synthesis. Russell
Sage Foundation, New York, USA.
Deeks J.J., Altman, D.G. & Bradburn, M.J. 2001. Statistical methods for examining
heterogeneity and combining results from several studies in meta-analysis, pp.285-312 in:
Eggar,M. Davey-Smith,G. & Altman D.G. (eds.) Systematic reviews in health care: Meta-
analysis in context. British Medical Journal Publishing Group, London, UK.
DerSimonian, R. and Laird, N. 1986. Meta-analysis in clinical trials. Controlled.

33
Clinical Trials 7: 177-188.
Donazar, J.A.., Hiraldo, F. & Bustamante, J. 1993. Factors influencing nest-site selection,
breeding density and breeding success in the bearded vulture (Gypaetus barbatus). Journal of
Applied Ecology 30: 504-514.
Dowling, B. & Weston, M.A. 1999. Managing a breeding population of the hooded plover
Thinornis rubricollis in a high-use recreational environment. Bird Conservation International 9:
255-270.
Duffy, D.C. 1979. Human disturbance and breeding birds. Auk 96: 815-816.
Dwyer, N.C. & Tanner, G.W. 1992. Nesting success in Florida sandhill cranes. Wilson Bulletin
104: 22-31.
Elias-Gerken, S.P. 1994. Piping plover habitat suitability on central Long Island, New York
barrier islands. MSc Thesis. Virginia Polytechnic Institute and State University, Blacksburg,
Virginia, USA.
Ellenberg, U., Mattern, T. & Seddon, P.J. 2009. Habituation potential of yellow-eyed penguins
depends on sex, character and previous experience with humans. Animal Behaviour 77: 289-296.
Evans, J. & Clark, N.A. 1993. Disturbance studies on Swansea Bay and the Burry Inlet in
relation to bird populations. A report by the British Trust for Ornithology under contract to the
Countryside Council for Wales, UK.
Fernández, C. & Azkona, P. 1993. Human disturbance affects parental care of marsh harriers and
nutritional-status of nestlings. Journal of Wildlife Management 57: 602-608.
Fernández, C., Azkona, P. & Donozar J.A. 1998. Density-dependent effects on productivity in the
griffon vulture Gyps fulvus: the role of interference and habitat heterogeneity. Ibis 140: 64-69.
Finney, S.K. Pearce-Higgins, J.W. & Yalden, D.W. & Langston, R.H.W. 2004. The effects of
recreational disturbance on two upland breeding bird, the golden plover Pluvialis apricaria and
the dunlin Calidris alpina. English Nature report reference FST20-11-011. English Nature,
Peterborough, UK.
Finney, S.K., Pearce-Higgins, J.W. & Yalden, D.W. 2005. The effect of recreational disturbance
on an upland breeding bird, the golden plover Pluvialis apricaria. Biological Conservation 121:
53-63.
Fiske, P., Rintamaki, P.T. & Karvonen, E. 1998. Mating success in lekking males: a meta-
analysis. Behavioral Ecology 9: 328-338.
Flemming, S.P., Chiasson, R.D. & Smith, P.C. 1988. Piping plover status in Nova-Scotia related
to its reproductive and behavioral-responses to human disturbance. Journal of Field Ornithology
59, 321-330.
Frid, A. & Dill, L.M. 2002. Human-caused disturbance stimuli as a form of predation risk.
Conservation Ecology 6: 1, 16 pp (online journal).

34
Giese, M. 1996. Effects of human activity on adelie penguin Pygoscelis adeliae breeding success.
Biological Conservation 75: 157-164.
Gill, F. & Donsker, D. (eds.) 2010. IOC World Bird Names (version 2.5).
http://www.worldbirdnames.org/ [Accessed 3 August 2010].
Gill, J.A. Surtherland, W.J. & Watkinson, A.R. 1996. A method to quantify the effects of humand
disturbance on animal populations. Journal of Applied Ecology 33: 786-792.
Gill, J.A., Norris,K. & Sutherland, W.J. 2001. Why behavioural responses may not reflect the
population consequences of human disturbance. Biological Conservation 97: 265-268.
Gil-Sánchez, J. M., Moleón, M., Otrero, M. & Bautista, J. 2004. A nine-year study of successful
breeding in a Bonelli's eagle population in southeast Spain: a basis for conservation. Biological
Conservation 118: 685-694.
Goldin M.R. & Regosin J.V. 1998. Chick behavior, habitat use, and reproductive success of
piping plovers at Goosewing Beach, Rhode Island. Journal of Field Ornithology 69: 228-234.
Green, R.E., Tyler, G.A. & Bowden, C.G.R. 2000. Habitat selection, ranging behaviour and diet
of the stone curlew (Burhinus oedicnemus) in southern England. Journal of Zoology 250: 161-183
Part 2.
Grubb, T.G. & King, R.M. 1991. Assessing human disturbance of breeding bald eagles with
classification tree models. Journal of Wildlife Management 55: 500-511.
Gurevitch, J. & Hedges, L.V. 1999. Statistical issues in ecological meta-analysis. Ecology 80:
1142-1149.
Gyuris, E. 2004. An experimental investigation of the effects of human intrusion into breeding
colonies of bridled terns Sterna anaethetus in the Great Barrier Reef. Pacific Conservation
Biology 9: 265-272.
Haworth, P.F. 1987. Moorland management and nature conservation in the South Pennines.
Council for National Academic Awards, UK.
Haworth, P.F. & Thompson, D.B.A. 1990. Factors Associated with the breeding distribution of
upland birds in the South Pennines, England. Journal of Applied Ecology 27: 562-577.
Henson, P. 1993. Breeding behavior of trumpeter swans (Cygnus buccinator) and implications
for management. PhD thesis, University of Minnesota, USA.
Henson, P. & Grant, T.A. 1991. The effects of human disturbance on trumpeter swan breeding-
behavior. Wildlife Society Bulletin 19, 248-257.
HMSO 2000. Countryside and Rights of Way Act 2000.
http://www.legislation.hmso.gov.uk/acts/acts2000/20000037.htm
HMSO 2003. Land Reform (Scotland) Act 2003.
http://www.opsi.gov.uk/legislation/scotland/acts2003/20030002.htm

35
Hockey, P.A.R. & Hallinan, J. 1981. Effect of human disturbance on the breeding behaviour of
jackass penguins Spheniscus demersus. South African Journal of Wildlife Research 11: 59-62.
Hockey, P.A.R. 1983. The distribution, population size, movements and conservation on the
African black oystercatcher Heamatopus moquini. Biological Conservation 25: 233-262.
Hockey, P.A.R. 1997. African black oystercatcher: Between the tides. African Birds and
Birding 2: 28-34.
Hockin, D., Ounsted, M., Gorman, M., Hill, D., Keller, V. & Barker, M.A. 1992. Examination of
the effects of disturbance on birds with reference to its importance in ecological assessments.
Journal of Environmental Management 36: 253-286.
Holland, P.K., Robson, J.E. & Yalden, D.W. 1982. The status and distribution of the common
sandpiper in the Peak District. Naturalist 107: 77-86.
Holmes, N.D., Giese, M., Achurch, H., Robinson, S. & Kriwoken, L.K. 2006. Behaviour and
breeding success of gentoo penguins Pygoscelis papua in areas of low and high human activity.
Polar Biology 29: 399-412.
Hoopes, E.M. 1993. Relationships between human recreation and piping plover foraging ecology
and chick survival. MSc Thesis. University of Massachusetts, Amherst, Massachusetts, USA.
Hoopes, E.M., Griffin, C.R., & Melvin, S.M. 1992. Relationships between human recreation and
piping plover foraging ecology and chick survival. Unpublished report. University of
Massachusetts, Amherst, Massachusetts, USA.
Hudson P. 1982. Red grouse production and management in relation to tourism, pp.45-54, in:
Hearn, K. (ed.). Moorland; wildlife conservation, amenity and recreation, RERG Report No.8.,
UK.
Hunt, G.L. Jr. 1972. Influence of food distribution and human disturbance on the reproductive
success of herring gulls. Ecology 53: 1051-1061.
Ikuta , L.A. & Blumstein, D.T. 2003. Do fences protect birds from human disturbance?
Biological Conservation 112: 447-452.
Jeffery, R.G. & Scott, H.A. 2005. Breeding success of African black oystercatchers Haematopus
moquini at Cape Agulhas, Western Cape, from 1978/79 to 2001/02. Ostrich 76: 8-13.
Joslin, G. & Youmans, H. (comps.) 1999. Effects of recreation on Rocky Mountain wildlife: a
review for Montana. Committee on effects of recreation on wildlife. Montana Chapter of the
Wildlife Society, USA. 307 pp.
Kålås, J.A., Fiske, P. & Saether, S.A. 1995. The effect of mating probability on risk taking: an
experimental study in lekking great snipe. American Naturalist 146: 59-71.
Keedwell, R. J. & Sanders, M.D. 2002. Nest monitoring and predator visitation at nests of banded
dotterels. Condor 104: 899-902.

36
Keller V.E. 1991. Effects of human disturbance on eider ducklings Somateria mollissima in an
esturine habitat in Scotland. Biological Conservation 58: 213-228.
Keller, V. 1995. Effects of human disturbance on birds - a literature review (Auswirkungen
menschlicher Storungen auf Vogel - eine Literaturubersicht). Ornithologische Beobachter 92: 3-
38.
Koryakin, A.S. 1987. Anthropogenic disturbance factors and survival of clutches in birds -
analysis of the problem with Somateria mollissima-L common eider taken as an example.
Zhurnal Obshchei Biologii 48: 706-716.
Lauro, B. & Tanacredi J. 2002. An Examination of predatory pressures on piping plovers nesting
at Breezy Point, New York. Waterbirds 25: 401-409.
Lafferty, K.D., Goodman, D. & Sandoval, C.P. 2006. Restoration of breeding by snowy plovers
following protection from disturbance. Biodiversity and Conservation 15: 2217-2230.
Lalkhen, A.G. & McCluskey, A. 2008. Statistics V: Introduction to clinical trials and systematic
reviews. Continuing Education in Anaesthesia, Critical Care & Pain Online 8: 143-146.
http://ceaccp.oxfordjournals.org/cgi/reprint/8/4/143.pdf
Lambeck, R.H.D., Goss-Custard, J.D. & Triplet P. (1996) Oystercatchers and man in the coastal
zone, pp.289-326, in: Goss-Custard, J.D. (ed.) The oystercatcher: from individuals to populations.
Oxford University Press, Oxford, UK.
Landis, R.J. & Koch, G.G. 1977. The measurement of observer agreement for categorical data.
Biometrics 33: 159-174.
Leseberg, A., Hockey, P.A.R. & Loewenthal, D. 2000. Human disturbance and the chick-rearing
ability of African black oystercatchers (Haematopus moquini): a geographical perspective.
Biological Conservation 96: 379-385.
Liley, D. 1999. Predicting the consequences of human disturbance, predation and sea-level rise
for ringed p lover populations. PhD Thesis, University of East Anglia, Norwich, UK.
Liley, D. 2002. Access to the countryside and bird conservation: priorities for research.
English Nature research report 485. English Nature, Peterborough, UK.
Liley, D. & Clarke, R.T. 2002. Urban development adjacent to heathland sites in Dorset: the
effect on density and settlement patterns of Annex 1 bird species. English Nature Research Report
463. English Nature, Peterborough, UK.
Liley, D. & Clarke, R.T. 2003. The impact of urban development and human disturbance on the
numbers of nightjar Caprimulgus europaeus on heathlands in Dorset, England. Biological
Conservation 114: 219-230.
Liley D. & Sutherland W.J. 2007. Predicting the population consequences of human disturbance
for Ringed Plovers Charadrius hiaticula: a game theory approach. Ibis 149: Issue s1, 82-94.
Loegering, J.P. & Fraser, J.D. 1995. Factors affecting piping plover chick survival in different
brood-rearing habitats. Journal of Wildlife Management 59: 646-655.

37
Lord, A., Waas, J.R. & Innes, J. 1997. Effects of human activity on the behaviour of northern
New Zealand Dotterel Charadrius obscurus aquilonius chicks. Biological Conservation 82: 15-
20.
Lord, A., Waas, J.R., Innes, J. & Whittingham, M.J. 2001. Effects of human approaches to nests
of northern New Zealand Dotterels. Biological Conservation 9: 233-240.
Mallord, J. 2005. Predicting the consequences of human disturbance, urbanisation and
fragmentation for a woodlark Lullula arborea population. PhD Thesis, University of East
Anglia, Norwich, UK.
Marshall, K. 2005. Capercaillie and recreational disturbance study: a report for CNPA, FCS and
SNH. http://www.cairngorms.co.uk/resource/docs/publications/31012006/CNPA.Paper.192.
Capercaillie%20and%20Recreational%20Disturbance%20Study.pdf
McClung, M.R., Seddon, P.J., Massaro, M. & Setiawan, A.N. 2004. Nature-based tourism
impacts on yellow-eyed penguins Megadyptes antipodes: does unregulated visitor access affect
fledging weight and juvenile survival? Biological Conservation 119: 279-285.
McConnaughey, J.L., Fraser J.D., Coutu S.D. & Loegering J.P. 1990. Piping plover distribution
and reproductive success on Cape Lookout National Seashore. Unpublished report to the
National Park Service, North Carolina, USA
Miller, S.G., Knight, R.L. & Miller, C.K. 1998. Influence of recreational trails on breeding bird
communities. Ecological Applications 8: 162-169.
Miller, S.G., Knight, R.L. & Miller, C.K. 2001. Wildlife responses to pedestrians and dogs.
Wildlife Society Bulletin 29: 124-132.
Mollet, P., Badilatti, B., Bollmann, K., Graf, R.F., Hess, R., Jenny, H., Mulhauser, B.,
Perrenoud, A., Rudmann, F., Sachot, S. & Studer, J. 2003. Numbers and distribution of
capercailie Tetrao urogallus in Switzerland 2001 and their changes in the 19th and 20th century.
Ornithologische Beobachter 100: 67-86.
Murison, G. 2002. The impact of human disturbance on the breeding success of nightjar
Caprimulgus europaeus on heathlands in south Dorset, England. English Nature Research Report
483. English Nature, Peterborough, UK.
Negro, J. J. & F. Hiraldo 1993. Nest-site selection and breeding success in the lesser kestrel Falco
naumanni. Bird Study 40: 115-119.
Niemuth, N. D. & Boyce, M.S. 2004. Influence of landscape composition on sharp-tailed grouse
lek location and attendance in Wisconsin pine barrens. Ecoscience 11: 209-217.
Nisbet, I.C.T. 2000. Disturbance, habituation and management of waterbird colonies -
commentry. Waterbirds 23: 312-332.
Nol, E. & Brooks, R.J. 1982. Effect of predator exclosures on nesting success of killdeer. Journal
of Field Ornithology 53: 263-268.

38
Ontiveros, D. 1999. Selection of nest cliffs by Bonelli's eagle (Hieraaetus fasciatus) in
southeastern Spain. Journal of Raptor Research 33: 110-116.
Patterson, M.E., Fraser, J.D. & Roggenbuck, J.W. 1991. Factors affecting piping plover
productivity on Assateague Island. Journal of Wildlife Management 55, 525-531.
Pearce-Higgins, J.W., Finney, S.K., Yalden, D.W. & Langston, R.H.W. 2007. Testing the effects
of recreational disturbance on two upland breeding waders. Ibis 149 (s1): 45-55.
Penny Anderson Associates 2003. Observations of wildlife made during closures of the
countryside during the 2001 foot and mouth disease epidemic. English Nature Research Report
486. English Nature, Peterborough, UK.
Picozzi, N. 1971. Breeding performance and bags of red grouse in relation to public access in the
Peak District National Park, England. Biological Conservation 3: 211-215.
Pienkowski, M.W. 1984. Breeding biology and population dynamics of ringed plovers
Charadrius hiaticula in Britain and Greenland: nest-predation as a possible factor limiting
distribution and timing of breeding. Journal of Zoology 202: 83-114.
Platt, J.B. 1977. The breeding behaviour of wild and captive gyrfalcons in relation to their
environment and human disturbance. PhD Thesis, Cornell University, USA.
Pollo, C.J., Robles, L., Seijas, J.M., - . & Otero, R. 2005. Trends in the
abundance of Cantabrian capercaillie Tetrao urogallus cantabricus at leks on the southern slope
of the Cantabrian Mountains, north-west Spain. Bird Conservation International 15: 397-409.
Ramakka, J. M. & Woyewodzic, R.T. 1993. Nesting ecology of ferruginous hawk in northwestern
New-Mexico. Journal of Raptor Research 27: 97-101.
Ratcliffe, D.A. 1990. Bird life of mountain and upland. Cambridge University Press, Cambridge,
UK.
Riffell, S. K., Gutzwiller, K.J. & Anderson, S.H. 1996. Does repeated human intrusion cause
cumulative declines in avian richness and abundance? Ecological Applications 6: 492-505.
Robertson, R. J. & Flood, N.J. 1980. Effects of recreational use of shorelines on breeding bird
populations. Canadian Field-Naturalist 94: 131-138.
Ruhlen, T. D., Abbott, S., Stenzel, L.E. & Page, G.W. 2003. Evidence that human disturbance
reduces snowy plover chick survival. Journal of Field Ornithology 74: 300-304.
Sandvik, H. & Barret, R.T. 2001. Effects of investigator disturbance on the breeding success of
the black-legged kittewake. Journal of Field Ornithology 72: 30-42.
Schauer, J.H.S. & Murphy, E.C. 1996. Predation on eggs and nestlings of common murees Uria
aalgae at Buff, Alaska. Colonial Waterbirds 19: 186-198.
Scheiner & Gurevich (eds.) 2001. Design and analysis of ecological experiments. Oxford
University Press, New York, USA.

39
Sculz, R. & Stock, M. 1993. Kentish plovers and tourists: competitors on sandy coasts? Wader
Study Group Bulletin 68: 83-91.
Sidaway, R. 1990. Birds and walkers. A review of existing research on access to the countryside
and disturbance to birds. Rambler‟s Association, London, UK.
Sidaway, R. 1994. Recreation and the natural heritage: a research review. Scottish Natural
Heritage, Edinburgh, UK.
Sidaway, R. 1995. Field experience of disturbance to birds: a pilot study. Scottish Natural
Heritage, Edinburgh, UK.
Steiner, W. & Parz-Gollner, R. 2003. Actual numbers and effects of recreational disturbance on
the distribution and behaviour of greylag geese (Anser anser) in the Neusiedler See – Seewinkel
National Park area. Journal for Nature Conservation 11: 324-330.
Stillman R.A., West A.D., Caldow R.W.G. & Le V Dit Durrell S.E.A. 2007. Predicting the effect
of disturbance on coastal birds. Ibis 149 (s1): 73-81.
Strauss, E. & Dane, B. 1989. Differential reproductive success in a stressed population of piping
plovers in areas of high and low human disturbance. American Zoologist 29: 42A.
Strauss, E.G. 1990. Reproductive success, life history patterns, and behavioral variation in a
population of piping plovers subjected to human disturbance. PhD Thesis, Tufts University,
Massachusetts, USA.
Strong, C.M., Spear, L.B., Ryan, T.P. & Dakin, R.E. 2004. Forster's tern, Caspian tern, and
California gull colonies in San Francisco Bay: habitat use, numbers and trends, 1982-2003.
Waterbirds 27: 411-423.
Strowger, J. 1998. The status and breeding biology of the dotterel Charadrius morinellus in
northern England during 1972-95. Bird Study 45: 85-91.
Summers, R.W. & Cooper, J. 1977. The population, ecology and conservation of the black
oystercatcher Haematopus moquini. Ostrich 48: 28-40.
Summers, R.W., Proctor, R., Thorton, M. & Avey, G. 2004. Habitat selection and diet of the
capercaillie Tetrao urogallus in Abernethy Forest, Strathspey, Scotland. Bird Study 51: 58-68.
Sutherland W.J., Armstrong-Brown, S., Armsworth, P. R et al. 2006. The identification of
100 ecological questions of high policy relevance in the UK. Journal of Applied Ecology 43: 617-
627.
Taylor E. 2002. Predation risk in woodlark Lullula arborea: the influence of recreational
disturbance, predator abundance, nest site characteristics and temporal factors. MSc Thesis,
University of East Anglia, Norwich, UK.
Taylor E. 2007. Stone curlews Burhinus oedicnemus and human disturbance: effects on
behaviour, distribution and breeding success. PhD Thesis, University of Cambridge, UK.

40
Taylor, K., Anderson, P., Taylor, R.P., Longden, K. & Fisher, P. 2005. Dogs, access and nature
conservation. English Nature research report No. 649. English Nature, Peterborough, UK.
Thompson, C.M. & McGarigal, K. 2002. The influence of research scale on bald eagle habitat
selection along the lower Hudson River, New York (USA). Landscape Ecology 17: 569-586.
Thompson, S.G. & Sharp, S.J. 1999. Explaining heterogeneity in meta-analysis: a comparison
method. Statistics in Medicine, 18: 2693-2708.
Tratalos, J.A., Gill, J.A. Jones, A., Showler, D.A., Bateman, I., Watkinson, A.R., Sugden, R. &
Sutherland, W.J. (in prep.) Factors affecting the distribution of coastal tourists and beach-nesting
birds on a regional scale: a GIS analysis.
Van der Zande, A.N. 1984. Outdoor recreation and birds: conflict or symbiosis? Impacts of
outdoor recreation upon density and breeding success of birds in dune and forest areas in the
Netherlands. PhD Thesis, Rijksuniversiteit, Leiden, Netherlands.
Van der Zande, A.N., Berkhuizen, J.C. Van Latesteijn, H.C., Ter Keurs, W.J. & Poppelaars, A.J.
1984. Impact of outdoor recreation on the density of a number of breeding bird species in woods
adjacent to urban residential areas. Biological Conservation 30: 1-39.
Verboven, N., Ens, B.J. & Dechesne, S. 2001. Effect of investigator disturbance on nest
attendance and egg predation in Eurasian oystercatchers. Auk 118: 503-508.
Verhulst, S., Oosterbeek, K. & Ens, B.J. 2001. Experimental evidence for effects of human
disturbance on foraging and parental care in oystercatchers. Biological Conservation 101: 375-
380.
Walker B.G., Boersma P.D. & Wingfield, J.C. 2005. Magellanic penguin. Physiological and
behavioral differences in Magellanic penguin chicks in undisturbed and tourist-visited locations
of a colony. Conservation Biology 19: 1571-1577.
Walker, B.G., Boersma, P.D. & Wingfield, J.C. 2006. Habituation of adult Magellanic penguins
to human visitation as expressed through behavior and corticosterone secretion. Conservation
Biology 20: 146-154.
Walker, B.G., Wingfield, J.C. & Boersma, P.D. 2008. Tourism and Magellanic penguins
(Spheniscus magellanicus): An example of applying field endocrinology to conservation
problems. Ornitologia Neotropical 19: Issue supp., 219-228.
Watson, J. J., Kerley, G.I.H. & McLachlan, A. 1996. Human activity and potential impacts on
dune breeding birds in the Alexandria coastal dunefield. Landscape and Urban Planning 34: 315-
322.
Watson, A. 1988. Dotterel Charadrius morinellus numbers in relation to human impact in
Scotland. Biological Conservation 43: 245-256.
Watson, J. W. 2004. Responses of nesting bald eagles to experimental pedestrian activity. Journal
of Raptor Research 38: 295-303.

41
Weston, M.A. & Elgar, M.A. 2005. Disturbance to breed-rearing hooded plover Thinornis
rubricollis: responses and consequences. Bird Conservation International 15: 193-209.
Weston, M.A. & Elgar, M.A. (2005) Responses of incubating hooded plovers (Thinornis
rubricollis) to disturbance. Journal of Coastal Research 23: 569-576.
Whitfield D.P., MacColl A.D.C., Holt S., Denny R., Gordon J., Pullan D. & Smith R. The
influence of human recreation on Eurasian dotterel Charadrius morinellus breeding in the
Scottish Highlands. I. The effect of disturbance. (Under review for Journal of Applied Ecology.)
Woodfield, E. & Langston, R. 2004(a). A study of the effects on breeding nightjars of disturbance
due to human access on foot to heathland. A report by the RSPB on behalf of the RSPB
and English Nature. The Royal Society for the Protection of Birds, UK.
Woodfield, E. & Langston, R. 2004(b). Literature review on the impact on bird populations of
disturbance due to human access on foot. RSPB research report No. 9, Project Ref. FST20-11-
011. The Royal Society for the Protection of Birds, UK.
Yalden, D.W. 1986. The further decline of black grouse in the Peak District 1975-1985.
Naturalist 111: 3-8.
Yalden, D.W. 1992. The influence of recreational disturbance on common sandpipers Actitis
hypoleucos breeding by an upland reservoir, in England. Biological Conservation 61: 41-49.
Yalden, D.W. & Pierce-Higgins, J.W. 1997. Density dependence and winter weather as factors
affecting the size of a population of golden plovers Pluvialis apricaria. Bird Study 44: 227–234.
Yalden, P. E. & Yalden, D.W. 1988. The level of recreational pressure on blanket bog in the Peak
District National Park, England. Biological Conservation 44: 213-277.
Yalden, D.W. & Yalden, P.E. 1989. The sensitivity of breeding golden plovers, Pluvialis
apracius, to human intruders. Bird Study 36: 49-55.
Yalden, D.W. & Yalden, P.E. 1990. Recreational disturbance of breeding golden plovers,
Pluvialis apracius. Biological Conservation 51: 243-262.
Yorio, P. & Boersma, P.D. 1992. The effects of human disturbance on Magellanic penguin
Spheniscus magellanicus behaviour and breeding success. Bird Conservation International 2:
161-173.

42
10. APPENDICES
Appendix 1. Characteristics of disturbance studies with potential data suitable for meta-analysis (* indicates used in meta-analysis).
Species
Reference
Ecological; habitat
& country/region
Method
Data
Outcome
Anatidae
Common eider
Somateria
mollissima
Bolduc &
Guillemette
(2003)
Nesting success in
vicinity of nesting
large gulls Larus spp.
Habitat: rocky shore
(Canada)
Experimental high (once every 3
days) vs. low (once every 15 days)
frequency human disturbance.
Each visit involved walking
through an eider colony and
deliberately flushing females off
nests; not deemed typical
disturbance from a walker (rather
„researcher disturbance‟), therefore
excluded from the analysis.
1 data point: probability
of eggs hatching under
high (0.32) and low
frequency (0.43) early-
season disturbances.
Upon flushing
incubating female
from nest
opportunities
presented for large
gulls to predate eggs.
Spheniscidae
Gentoo penguin
Pygoscelis papua
*Holmes et
al. (2006)
Incubation period to
chicks joining crèche;
(6-8 weeks in 2002).
Habitat: beach
(Australian
Antarctic)
49 breeding colonies, 2 counts to
ascertain: i) no. of breeding pairs
during incubation/guard phase; ii)
number of chicks raised to crèche
age. Number of chicks reared
compared between areas „on-
station‟ (high human activity, inc.
some vehicular disturbance) and
„off-station' (low human
disturbance).
1 data point: mean
productivity of chicks
reared to crèche age.
1.43 chicks/pair „on
station‟ ; 0.9 chicks/pair
„off station‟
No. of chicks
raised/pair higher in
colonies with greater
human disturbance.
*Cobley &
Shears
(1999)
Chick weight at 20
days; 1996-97 austral
summer. Habitat:
Tourists excluded from 4 colonies
(control), but allowed to walk
around 6 colonies under
1 data point: weight of
chicks at 20 days in a
disturbed (n = 10) and
No difference in
average chick weight
>< disturbed and

43
low-lying islet
(Antarctica)
supervision (disturbance
treatment).
control colony (n = 12)
control colonies.
Adelie penguin
Pygoscelis adeliae
*Giese
(1996)
Chick survival/nest
up to 2 weeks of age,
10 Nov 1993 to 18
Jan 1994. Habitat:
rocky coast
(Antarctica)
Six colonies (3 larger, mean 70
nests; 3 smaller, mean 44 nests)
exposed to disturbance treatments
(nest checks and recreational
visits) vs. no disturbance (control).
Breeding success examined in
terms chick survival to 2 weeks old
(estimated to within 48 h). This
permits only a conservative
estimate of overall nest failure, but
chicks were unmarked thus
difficult to determine fate at later
stages.
2 data points: 1) No. of
nests with at least 1
chick raised to 2 weeks
old in smaller colonies;
2) no. of nests with at
least 1 chick raised to 2
weeks old in larger
colonies).
Smaller colony size:
5/37 (14%) nests
(disturbed) and 31/37
(84%) nests (control)
with at least 1 chick.
Larger colony size:
62/75 (83%) nests
(disturbed) and 58/63
(92%) nests (control)
with at least 1 chick.
Yellow-eyed
penguin
Megadyptes
antipodes
*McClung
et al. (2004)
Fledging weight and
fledglings/pair; 2001-
2002 breeding
season.
Habitat: beach (New
Zealand)
Fledging weight estimated by
weighing chicks within approx. 4
weeks before first entering the sea
at five beaches: one beach
categorised „high level of human
disturbance‟; three „low to
moderate disturbance‟; and one
„least disturbed‟.
Number of young successfully
fledged/pair in a more disturbed
(n=19 breeding pairs) vs. less
disturbed (n=14 pairs) area
2 data points: Mean
fledgling weight of
chicks related to the
degree of human
disturbance, either high
(1 beach) or least
disturbed (1 beach).
Low-moderate levels of
disturbance excluded in
this analysis).
Fledging success
High disturbance
beach: mean chick
weight 5.32 kg (SD
0.602).
Least disturbed
beach: mean chick
weight 6.08 kg (SD
0.794).
High disturbance
0.95/pair; less
disturbed 0.79/pair
Magellanic
penguin
Spheniscus
magellanicus
*Yorio &
Boersma
(1992)
Fledgling weight; no.
of chicks/active nest
Habitat: beach
(Argentina)
Fledging weight estimated by
weighing chicks in a tourist (more
disturbed) vs. non-tourist (less
disturbed) area.
2 data points: mean
fledgling weight of
chicks and chicks
fledged/active nest,
related to the degree of
human disturbance.
Mean fledging
weight similar in
tourist area 2.40 kg
(SD 0.35; n=50 nests)
vs. non-tourist area
2.33 kg (SD 0.33;

44
Breeding success (chicks
fledged/active nest) in a tourist
(more disturbed) vs. non-tourist
(less disturbed) area.
n=50).
Mean number of
chicks/pair similar in
tourist area 1.06
(n=36 nests) vs. non-
tourist area 1.04
(n=54).
Pelicanidae
Brown pelican
Pelicanus
occidentalis
*Anderson
& Keith
(1980)
Young fledged/nest
built (data from 3
breeding seasons,
1971, 1972, 1974).
Habitat: beach (USA)
Young fledged compared ><
disturbed area (nests disturbed by
human visitors at egg/small young
stage i.e. humans had approached
nesting birds, but not always
walking amongst active nests) and
undisturbed nests.
1 data point: Mean
productivity (young
fledged/pair) of
disturbed vs.
undisturbed nests.
Productivity much
lower, 0.26
fledglings/pair
(n=2,663 nests) in
disturbed area vs.
1.33 (n=3,328) in
undisturbed area.
Phasianidae
Black grouse
Tetrao tetrix
*Baines &
Richardson
(2007)
Hatching success.
Habitat: moorland
(UK)
Three experimental disturbance
treatments: no disturbance (low),
fortnightly disturbance (moderate)
or twice weekly disturbance
(highest) by walker.
1 data point: %
hatching success of no
disturbance vs. highest
disturbance.
Hatching success
similar between no
disturbance 48%
hatch success (n=22
nests) vs. highest
disturbance 46%
hatch success (n=33).
Charadriidae
Eurasian golden
plover Pluvialis
apricaria
*Finney et
al. (2005)
Proximity of nesting
pairs to a major
footpath (Pennine
Way) over 12
breeding seasons
(1986-1998). Habitat:
moorland (UK)
Surveys during nesting period
recording fledging success of
broods (to the nearest 100 m grid
square) from 100 m to 1,200 m.
1 data point: brood
survival to fledging in
relation to nearest
(within 100m) distance
of territory, and furthest
(1,100-1,200m) from
footpath. Raw residuals
from logistic regression
control for significant
effects of habitat type
and date, plotted at 100
m intervals.
Brood survival to
fledging higher at
closer distance to
path (20%) vs. at
furthest distance from
path (10%) surveyed

45
Haematopodidae
Eurasian
oystercatcher
Haematopus
ostralegus
Verhulst et
al. (2001)
Proportion of time
eggs incubated over 3
days of observation
in 1999. Habitat:
saltmarsh
(Netherlands)
Three days of observation of 4
pairs, each day observing during 1
low tide period. First and third day
used as control, second day
foraging adults actively pursued
and pushed off territory during 1
low tide cycle.
1 data point:
proportion of time eggs
incubated when adults
not disturbed (foraging
in feeding territory),
and when pursued and
pushed out of feeding
territory. (Not used in
analysis as lacking
comparable data).
Disturbance
significantly reduced
the proportion of time
that eggs were
incubated.
Common sandpiper
Actitis hypoleucos
*Yalden
(1992)
No. of hatching
territories and
fledging territories
around shoreline over
2 breeding seasons,
1989 and 1990.
Habitat: upland
reservoir (UK)
Alternate Saturdays and Sundays
devoted to either sandpiper surveys
or angler counts (i.e. measure of
disturbance) around reservoir
shoreline.
2 data points: no. of
hatching territories and
no. of fledging
territories. Comparison
of breeding success for
territories between
„quiet‟ (<6 people/km
of shoreline/survey
visit) and „busy‟ >6
people/km/ visit).
In busy territories
(n=17) 71% of nests
hatched; in quiet
territories (n=40)
58% hatched.
In busy territories
(n=23) 65% fledged
young; in quiet
territories 83%
fledged young.
Common ringed
plover Charadrius
hiaticula
*Liley
(1999)
Breeding parameters
including territory
establishment, nest
and chick survival,
and fledging success
in relation to human
disturbance; over
three years, 1996-
1998. Habitat: beach
(UK)
Various studies undertaken on
beaches/beach front occupied by
breeding plovers
4 data points:
1) survival through
incubation; daily nest
survival rate at highest
human disturbance
level vs. lowest.
2) mean % of eggs
fledging in areas with
human access (eggs
prone to trampling) vs.
no access.
3) Effects of
disturbance intensity
(people counts within
120m beach sections)
1) daily nest survival
rate 68% (n=16 nests)
at highest disturbance
vs. 94% (n=139)
lowest level.
2) 4.55% of eggs
fledged in areas with
human access (n=36
nests) vs. no access
12.64% (n=17).
3) Nest density
declined with
increasing numbers

46
*Pienkowski
1984
Hatching success
Habitat: beach (UK)
Hatching success of nests recorded
in areas categorised according to
three levels of human visitation:
high (100+ human visitors/day);
moderate (up to 50 visitors/day);
low (c.5 visitors/day).
on nest density.
(Excluded from
analysis as too related
to other variables and
insufficient comparable
data from other
studies).
4) Time chick
foraged/30min
observation when
people within 100m of
brood cf. when no
people within 100m
(data point excluded
due to lack of
comparable data).
1 data point: hatching
success in high
disturbance (100+
visitors/day) vs. low
disturbance (c.5
visitors/day) areas.
of people.
4) Chick foraging
time reduced in areas
with more people but
this had no effect on
growth or survival to
fledging.
Nest survival to
hatching averaged
50.5% (n=50 nests)
in low disturbance
area (27% moderate
disturbance) and
1.7% (n=55) in high
disturbance area.
Piping plover
Charadrius
melodus
*Flemming
et al. (1988)
Study over 4
breeding seasons
(1979-83). Habitat:
beach (Canada)
Levels of disturbance were
quantified over five years (1979-
1983) by recording positions of
people, their footprints and vehicle
tracks. Surveys (4 breeding
seasons) recorded number of
chicks surviving/nest attempt to 10
days old and to 17 days old
(fledging) on beaches subject to
high and low disturbance.
2 data points: Chicks
surviving to 10 days old
/nest attempt and chicks
surviving to
fledging/pair, in areas
of high vs. low
disturbance (means
over 4 breeding
seasons).
Chicks survival to 10
days old was 1.2
chicks/pair (n=18
nests) in high vs. 1.8
chicks/pair (n=24) in
low disturbance
areas.
Number of chicks
fledging was 0.5/pair
(n=16) in high vs.

47
1.8/pair (n=21) in
low disturbance
areas.
Snowy plover
Charadrius nivosus
*Ruhlen et
al. (2003)
Chick mortality at
high compared to low
disturbance days.
Habitat: beach (USA)
Surveys recorded proportion of
chicks lost at weekends/holidays
(higher disturbance) cf. chicks lost
on weekdays (lower disturbance)
1 data point: cumulative
mean percent chick
survival on high
disturbance vs. low
disturbance, days
Of the initial 83
nests, a higher
proportion of chicks
survived on low
disturbance days
(65%) vs. high
disturbance days
(35%).
Hooded dotterel
Thinornis
rubricollis
*Dowling &
Weston
(1999)
Monitoring of plover
breeding parameters
over 7 breeding
seasons (1991-1998).
Habitat: beach
(Australia)
Surveys undertaken to determine:
proportion of nests that hatched
and causes of clutch loss on beach
vs. dunes;
mean number of fledglings/clutch
at nests on beach with „least
managed conditions‟ (i.e. walkers
and their dogs on a lead, allowed at
all times vs. „most intensive
management regimes‟ (i.e. no
dogs; Plover Watch; restricted
access);
proportion of clutches hatching on
beaches where dogs and people
allowed (more disturbed) cf. where
people allowed but not dogs (less
disturbed).
3 data points:
1) hatching success of
nests on beach (more
disturbed) vs. on dunes
(less disturbed).
2) fledging success of
beach nests under least
managed vs. most
intensive management
regimes.
3) proportion of
clutches hatching on
beaches where dogs and
people allowed cf.
where people allowed
but not dogs.
1) Of 41 beach nests
10 (24.4%) hatched
(21; 51.2%, were
trampled). Of 56
dune nests 23
(41.1%) hatched (12;
21.4%, were
trampled).
2) Of 49 nests on
„least managed‟
beaches, no chicks
fledged; of 40 nests
within sections under
most intensively
managed, 0.53
fledged/nest.
3) 0% of clutches
(n=49) where dogs
and people allowed
vs. 40% (n=5) where
people allowed but
not dogs hatched.

48
Weston &
Elgar (2005)
Disturbance effects
of brood-rearing on
chicks, 1995-1998.
Habitat: beach
(Australia)
Each brood observed on days of
relatively high disturbance
(weekend or public holiday) and
relatively low disturbance (often a
non-public-holiday weekday).
Number of human/brood
encounters and time chicks spent
hiding recorded.
1 data point: time
chicks hiding on
relatively disturbed vs.
relatively undisturbed
days. (Excluded from
analysis as comparable
data lacking).
Chicks unable to
solicit brooding when
hiding. Number of
mins spent hiding/h
significantly higher
on relatively
disturbed (30.1 ±
15.6 min) compared
to relatively
undisturbed (22.5 ±
14.6 min), days.
Laridae
Least tern
Sterna antillarum
*Burger et
al. (1995)
Effects of disturbance
on fledging success at
tern colonies (1983-
1990). Habitat: beach
(USA)
Surveys undertaken to assess
success in relation to human
disturbance categorised as: i)
primarily ecotourists
(birdwatchers); ii) primarily other
types of human disturbances (sun-
bathers, joggers, fishermen –
considered most pertinent to the
present review); iii) few ecotourists
and few disturbances
2 data points:
1) Percentage of pairs
raising >0.5 young/pair
in more frequently
disturbed colonies (ii)
vs. colonies with few
disturbances (iii).
2) Percentage of pairs
raising 0.1 - 0.5
young/pair
1) 29% of pairs
(n=12 colonies)
raised >0.5
young/pair in more
frequently disturbed
colonies vs. 73%
(n=13) with few
disturbances.
2) 32% of pairs
(n=13 colonies)
raised 0.1-0.5
young/pair in more
frequently disturbed
colonies vs. 27%
(n=5) with few
disturbances.
Bridled tern
Onychoprion
anaethetus
*Gyuris
(2004)
Effect of low-
moderate disturbance
on breeding success
at colonies on Great
Barrier Reef islands
(1995-1998).
Habitat: beach
(Australia)
Two levels of disturbance
schedules implemented over 2-3
breeding seasons: i) 5 sites
monitored every fourth day to
record status of eggs/chicks (2-3
people walked through colony,
ringed and weighed chicks;
disturbance time kept to a
minimum); ii) 3 of the sites
2 data points:
1) Mean chick weight
at 12-13 days at
„monitored only sites‟
vs. „disturbance sites‟.
2) Mean chick weight at
20 days (fledging) at
„monitored only sites‟;
1) At monitored only
sites mean chick
weight at 12-13 days
(69.3g) significantly
less than disturbance
sites (77.4g).
2) At monitored only
sites mean chick

49
(„disturbance sites‟) also disturbed
experimentally to simulate low-
moderate level visitation (visitor
intrusion for 3 h/week)
experienced on many islands.
vs. „disturbance sites‟.
weight at 21-22 days
(103.5g) but not
significantly less than
disturbance sites
(106.8g)
Black-legged
kittiwake
Rissa tridactyla
*Beale &
Monaghan
(2004)
Breeding success
during 2002 breeding
season. Habitat: sea
cliffs (UK)
106 nests selected. Fledging
success recorded. Number of
people along paths in vicinity
recorded. Disturbance parameters
(previously identified in as
potentially significant) affecting
nest success modelled.
1 data point: effect of
increased vs. decreased
visitor numbers on
fledging success.
40% increase in
visitor numbers, c.2%
fledging success.
50% decrease in
visitor numbers
c.96% fledging
success.
Heermann‟s gull
Larus heermanii
*Anderson
& Keith
(1980)
Number of
young/100 adults at 2
colonies in 1974
breeding season
Habitat: beach (USA)
3 human disturbance intensities (no
known disturbance, moderate and
heavy). Number of young then
related to degree of disturbance.
1 data point: Number of
young fledged/100
adults at heavy vs. no
known disturbance
colonies.
4.5 young/100 adults
(n=1,281 adults) at
heavy vs. 17.7/100
adults (n=1,421
adults) at no known
disturbance colonies.
American herring
gull
Larus
smithsonianus
*Hunt
(1972)
Eggs hatching and
young fledged/nest at
colonies on islands
during 1968-1970
breeding seasons.
Habitat: coastal islets
(USA)
Percentage of chicks hatching and
young fledged/nest recorded at
colonies on islands subject to more
vs. less frequent visitor disturbance
(mainly picnickers); measured
subjectively on basis of „number of
old fireplaces, beer cans and picnic
groups‟ encountered during visits
2 data points:
1) Percentage of chicks
hatched/eggs laid on
more vs. less disturbed
island.
2) Number of fledglings
produced/nest on more
vs. less disturbed
island.
1) 22% of eggs
hatched on more
disturbed (n=375
nests) vs. 49.5% on
less disturbed (n=
483) island.
2) 0.288
fledglings/nest
on more disturbed vs.
0.606/nest on less
disturbed island.
Alcidae
Common guillemot
Uria aalge
*Beale &
Monaghan
(2004)
Breeding success
during 2002 breeding
season. Habitat: sea
cliffs (UK)
241 nests selected. Fledging
success recorded. Number of
people along paths in vicinity
recorded. Effects of parameters
affecting nest success modelled.
1 data point: effect of
increased vs. decreased
visitor numbers on
fledging success.
40% increase in
visitor numbers,
c.36% fledging
success.

50
50% decrease in
visitor numbers
c.87% fledging
success.
Peregrine falcon
Falco peregrinus
*Brambilla
et al. (2004)
Fledging success of
cliff-nesting
peregrines in 2002
and 2003 breeding
seasons. Habitat:
inland cliffs (Italy &
Switzerland)
Proportion of pairs (=nests)
producing fledged young on cliffs
with climbers only (n=2 pairs) cf.
those on cliffs with climbers and
ravens Corvus corax (n=5), and no
climbers or ravens (n=14).
1 data point: Nesting
success (young reared
to fledging) at cliff sites
with climber
disturbance only (i.e. no
raven present) vs. no
human disturbance.
50% of nests (n=2)
producing fledglings
on cliffs with
climbers; 79% of
nests (n=14)
producing fledglings
on cliffs with no
climber disturbance.
Western marsh
harrier
Circus aeruginosus
*Fernández
& Azkona
(1993)
Effects of low levels
of human disturbance
on parental care and
nestling nutritional
status, 1991 breeding
season. Habitat:
marsh (Spain)
Changes in reproductive activities,
nutritional condition and fledging
success monitored.
1 data point: Fledging
success of pairs subject
to low levels of human
disturbance vs. no
human disturbance.
In nests (n=6) subject
to low levels of
disturbance 64% (25
eggs laid, 16 chicks)
fledged; Similarly in
nests (n=5) subject to
no disturbance 67%
(24 eggs laid, 16
chicks) fledged.
Passeriformes
Woodlark
Lullula arborea
Mallord
(2005)
Density of breeding
pairs/ha of suitable
habitat in 2002 and
2003. Habitat:
heathland (UK)
Density of breeding pairs/ha of
suitable habitat recorded at
heathland sites and related to
observed levels of human visitation
(people/survey/ha).
1 data point: Density of
breeding pairs/ha at
sites (n=3) with low
disturbance
(<0.01people/survey/ha
) cf. density at sites
(n=5) with highest
disturbance (>0.1
people/survey/ha).
Comparable data
lacking from other
studies therefore
excluded from analysis.
At low disturbance
the density of
woodlark pairs was
around 0.6 pairs/ha of
suitable habitat, at the
highest disturbance
level densities were
0.1-0.2 pairs/ha.

51
Western
meadowlark
Sturnella neglecta;
Vesper sparrow
Pooecetes
gramineus;
Grasshopper
sparrow
Ammodramus
savannarum
Miller et al.
(1998)
Number and distance
of nests from trails
over 5 weeks in 1994
and 7 weeks in 1995.
Habitat: grassland
(USA)
Nests were located from the edge
of trails out to 200 m, ensuring
equal search effort at all distances.
Probability that a nest will occur at
a given distance from trails and
control transects. Due to small
sample sizes of nests for some
species, analyses of individual
species not possible.
2 data points:
1) predicted probability
that a nest will occur at
0 m vs. at 200m
2) Predicted probability
that a nest will survive
in grassland one day at
increasing distance
from trails.
Comparable data
lacking from other
studies therefore
excluded from analysis.
1) Western
meadowlark and
grasshopper sparrow
were less likely to
nest near trails: 0.28
probability of a nest
at 0m; 0.5 probability
of nest at 200m.
2) Probability that a
nest (all 3 species)
would survive one
day (n = 163 nests;
1,954 nest days)
related to distance
from trails; the
further the distance
from a trail, the
higher the probability
of survival.

52
Appendix 2. Summaries of studies of human access disturbance on breeding
ground-nesting and cliff-nesting birds.
Species accounts are arranged within four habitat categories: i) beaches, rocky shores and
marine islands; ii) cliffs; iii) heaths and lowland grassland; and iv) moorland, tundra and
mountain.
BEACHES, ROCKY SHORES and MARINE ISLANDS
Gentoo penguin Pygoscelis papua
Holmes et al. (2006) investigated the behaviour and breeding success of gentoo penguins
in areas of high and low human activity on sub-Antarctic Macquarie Island (Australia).
The area of high human activity encompassed the Australian Antarctic Program station
limits, within which penguins were exposed to general pedestrian and vehicle activity as
required to run the station, and also controlled human approaches. Low activity areas
were beyond the station limits where human visitation, except for approach experiments,
was kept to a minimum during the breeding season (from egg-laying onwards).
Approach experiments were conducted on penguins nesting at the edge of colonies as
these were exposed to the greatest potential pedestrian disturbance, and this allowed for
the influence of nest location to be standardized. The approach procedure comprised a
before, during and after design to allow repeated measures of behavioural response as a
person walked to within 5 m (the closest approach) of the penguins. In low disturbance
colonies, gentoos displayed significantly higher levels of vigilance and threat display
behaviour when approached. In contrast, those within the station limits (exposed to daily
high human activity) showed little noticeable response to approaches, other than some
evidence of increased vigilance and decreased resting, but not much different to pre-
approach levels, suggesting that to a greater or lesser degree, these birds were habituated
to this form and level of disturbance.
Breeding success was estimated by taking two counts at 49 of the 50 gentoo colonies on the
island. The first count (during the incubation/guard phase) ascertained the number of
breeding pairs. The second took place during crèche (when older chicks group together) to
determine the number of chicks raised to crèche-age (about 6-8 weeks old). Average on-
station breeding success was greater than off-station, however variation over-lapped with
off-station colonies, and those beyond the station limits on part of the island had the highest
density of colonies and highest breeding success. Factors other than human disturbance,
such a habitat quality and presence of southern elephant seal Mirounga leonina harems
(which disrupted breeding activity) were found to be important and influenced breeding
success.
Cobley and Shears (1999) looked at the effect of visitor disturbance on gentoos over one
breeding season at the popular ecotourist site of Goudier Island on the Antarctic Peninsula.
Breeding performance was compared between colonies visited by tourists (35-55 people
every 1-2 days) with nearby undisturbed colonies. There was no difference between the
disturbed and undisturbed colonies in the proportion of birds that laid, in hatching success
or proportion of single chick broods. There was also no difference in chick weight or
survival up to 20 days of age, and survival to crèche age was high and similar between the
two groups. Gentoos only became established as a breeding species on Goudier Island in

53
1985, since when the penguin population has grown rapidly. Human disturbance from
regulated tourist visits appears not to be constraining population growth.
Adelie penguin Pygoscelis adeliae
Giese (1996) compared adelie penguin breeding success at colonies subject to different
types and intensity of human activity within one breeding season in the Vestfold Hills,
Antarctica. Three larger (about 70 nests each) and three smaller (about 44 nests each)
colonies were exposed to one of three treatments (a treatment replicated at one colony of
each size): nest checking (nests visited every second day for about 15 min); recreational
visits (two to four, 10-min visits every day by two people walking slowly around the
colony periphery 5 m from its edge, kneeling and taking photographs, thus mimicking
tourist visitor intensity and activities); and no disturbance.
Hatching success and chick survival was highest in the two undisturbed colonies. In the
smaller colonies exposed to disturbance treatments, hatching success and survival were
significantly reduced: hatching success was 35% lower at the colony exposed to nest
checking and 47% lower for recreational visits compared with the undisturbed colonies;
chick survival was 72% and 80% less respectively. The two disturbance treatments also
reduced hatching and chick survival at the larger colonies but not significantly so. South
polar skua Catharacta maccormicki predating on eggs exposed during human disturbances
at the smaller colonies is given as the most likely cause of egg loss, although no data is
presented to support this.
Yellow-eyed penguin Megadyptes antipodes
McClung et al. (2004) explored the relationship between human disturbance and yellow-
eyed penguin fledging weight and chick survival at colonies on the Otago Peninsula,
South Island, New Zealand. Five breeding areas with different levels of visitor frequency
were compared. In 2002 at one site with high tourist numbers, fledging weights were
significantly lower than chicks in an area with no tourists. Whether fledging weight is a
predictor of juvenile survival was investigated using long-term (1981-2000) data of re-
sightings of ringed (banded) birds. This indicates that survival probability was positively
correlated with weight at fledging. Fledging weight is influenced by many factors but
results suggest that higher tourist visitation levels may have a detrimental effect on chick
fledging weight and hence longer-term survival. Ellenberg et al. (2009), investigated
habituation potential of yellow-eyed penguins in southern New Zealand. Individual birds
differed significantly in both their initial stress response and habituation potential upon
human approach (some habituated to short and consistent approaches, others did not).
The authors conclude that this species appears unsuitable for unregulated tourist visits at
nest sites.
African (Jackass) penguin Spheniscus demersus
Hockey and Hallinan (1981) assessed the effect of human disturbance on breeding African
penguins at Jutten Island, Saldanha Bay, South Africa. Two types of disturbance were
assessed: a person walking through a low-density colony (nests approx. 4 m apart) and
approach on foot to a high density colony (nests approx. 1 m apart). Three low-density
colonies each had a different level of human passage along a transect line: walked daily

54
(over seven days), walked every 2 hours (between 08:30-16:30 h on two consecutive days);
and walked once every hour (between 09:00-17:00 h on two consecutive days). Two types
of approach were made to high density colonies: two colonies (one coastal, one inland)
were approached gradually to 10 m of the colony periphery (five stages, 10 min at each,
recording bird behaviour); three colonies were approached directly (walking to 30, 20 or 10
m from the colony periphery). Adult penguins reacted most strongly to a direct approach,
whereas chicks reacted most to a gradual approach. At coastal colonies, approaches led to a
high exodus of birds with many leaving the colony (presumably to the sanctuary of the
nearby sea where they felt safer) whilst no exodus of birds at inland colonies occurred,
perhaps (although not stated) as they had no safe refuge to flee too.
Walking through colonies led to egg loss due to predation by kelp gulls Larus dominicanus,
as incubating penguins sometimes temporarily abandoned their eggs at the approach of a
person. Nest-prospecting penguins were scared away and were absent altogether after the
fourth day of disturbance. These disturbance experiments were only conducted over 2-7
days, and the authors suggest that if such disturbance was continuous throughout the
duration of the breeding season it could detrimentally affect reproductive success.
Magellanic penguin Spheniscus magellanicus
Yorio and Boersma (1992) looked at the effects of human disturbance on magellanic
penguin behaviour and breeding success at Punto Tombo on the Patagonian coast of
Argentina. Responses of penguins were investigated in this large (225,000 pairs) colony in
four areas exposed to different forms of disturbance: a tourist area where visitors can walk
amongst nests; within 15 m of a 1 km-long access road; a restricted area with no access
except rare visits by rangers/researchers; and a scientific study area where nest checks are
undertaken. Penguins in tourist areas were more tolerant of human approaches (allowing a
significantly closer approach before eliciting threat and defence displays) than those in
areas seldom visited. During incubation, to assess whether adults temporarily abandoned
their eggs, controlled approaches were undertaken in two different habitats within the
colony. A total of 286 „burrow‟ nests and 82 „bush‟ nests were approached along transect
lines; no penguin abandoned its eggs. Breeding success (number of young fledged/active
nest) and fledgling weights were similar in all four areas.
Walker et al. (2005) examined behavioural and physiological differences in chicks living
in either tourist-visited or undisturbed areas of the Punta Tombo breeding colony. Newly
hatched chicks in visited areas had higher corticosterone stress responses than newly
hatched chicks in undisturbed areas (baseline levels were similar). By 40-50 days old and
around fledging time, tourist-visited chicks did not move away when approached,
whereas undisturbed chicks fled (when approached to no closer than 9 m). Although it is
unknown whether chicks raised in visited areas suffer negative consequences due to an
elevated stress response at hatching, they exhibit behavioural habituation to human
approach by fledging age. A subsequent study (Walker, Boersma & Wingfield 2006)
showed that habituation by adult magellanic penguins to human visitation is rapid.
Walker et al. (2008) reviewed studies examining how endocrine stress physiology of
magellanic penguins is modified by tourist visitation. In a colony showing few outward
negative behavioural or other population-level effects due to human disturbances, some

55
potentially significant detrimental physiological modifications were apparent. The long-
term consequences are unknown but raise concerns that there may be negative impacts
due to visiting tourists.
Brown pelican Pelicanus occidentalis
Anderson and Keith (1980) looked at the effect of human recreation on beach-nesting
brown pelicans in Baja California, Mexico. Breeding productivity in disturbed sub-
colonies (humans in full view and closely approaching nesting birds) was compared with
that of nearby undisturbed „control‟ areas. Even only one disturbance event (whether
caused by casual visitors or researchers) early in the nesting season had a severe effect;
over three years average productivity (fledged young) was 80% less in disturbed areas.
Detrimental disturbance effects manifested as loss of eggs and young following short- or
long-tem abandonment by adults, and subsequent predation by e.g. western gull Larus
occidentalis and commom raven Corvus corax. Gulls attacked even large chicks (up to 4-
weeks old) in the absence of their parents, forcing them to regurgitate food or causing
injuries resulting in later death. Some losses may have been attributable to hyper- or
hypothermia, and trampling by adults and larger young. In addition, some larger, more
mobile young became impaled and died in prickly pear Opuntia cacti in the confusion
elicited by disturbance events. Disturbance early in the breeding season often had a lasting
effect, with the disturbed sub-colony abandoned or remaining only thinly occupied
throughout the remainder of the breeding season.
Severe population declines can result from excessive human visitation as exhibited on Isla
San Martin, Baja California (Anderson & Keith 1980). In 1969 the breeding colony
comprised 800 pelican pairs but declined rapidly in response to disturbance and pollution.
Ecotourist visits occurred almost weekly throughout the early (most sensitive) breeding
period, especially after 1972. At this time lessening pollution may have led to expected
recovery but disturbance continued and by 1975 the colony had been extirpated.
Common eider Somateria mollissima
Bolduc and Guillemette (2003) investigated the effects of frequency and timing of
disturbance, and the abundance of nearby avian nest-predators (great black-backed gull
Larus marinus and American herring gull L.(argentatus) smithsonianus on eider nesting
success at Michigan National Park Reserve, Quebec, Canada. Some 3,500 nests were
surveyed on islands only rarely visited by recreationists during the nesting period. Three
disturbance treatments were applied to a sample of nests and the incubating female: high
frequency visits (once every three days) or low frequency visits (once every 15 days)
commencing early in the incubation period; and high frequency visits starting late in the
incubation period. A disturbance to each nest included flushing the female off the nest.
Visits were designed to simulate tourists or researchers walking through a nesting colony.
Disturbance treatments and nearby gull nest density had a significant effect on eider nesting
success. The authors suggest that the main consequence of disturbance was to produce
opportunities for gulls to predate unattended eggs, although no predation data is presented.
Probability of nesting success was similar under the high and low frequency early-season
disturbances (0.32 and 0.43 respectively). In contrast, high frequency visits starting later in
the season resulted in a significant higher nesting success probability (98%) than the high

56
frequency early treatment. Most nest failures occurred after the first disturbance for all
treatments but was lowest for the high frequency late disturbance treatment (11% dropping
to almost zero on subsequent visits), compared to high frequency early visits (26%) and
low frequency early visits (33%). In the latter two treatments a small decrease was noted
over the next 2-3 visits of around 5%. The authors therefore recommend that visits by
researchers/wildlife managers to eider colonies should be as late as possible in the
incubation period, and visits should be avoided to colonies associated with high densities of
potential egg predators. In terms of this present study therefore, visitation to nesting areas
by walkers should likewise be avoided at such times in similar situations.
Keller (1991) observed that female eiders and their ducklings on the Ythan estuary in
Scotland were frequently disturbed by recreational activities, both when onshore and when
feeding in the water. Fishermen, people walking along the shoreline and dogs, caused more
disturbances than water-based activities (windsurfers and rowing boats). Disturbance
affected eider crèches (ducklings and attending females) for up to 35 min, presumably
resulting in energy expenditure and loss of foraging time. Disturbance of small ducklings
led to increased predator encounters (mostly large gulls) as ducklings were sometimes split
from the adult females following disturbance events.
Eurasian oystercatcher Haematopus ostralegus
Tratalos et al. (in prep.) undertook an intensive survey of coastal beaches of Norfolk and
Suffolk (southeast England), mapping locations of nesting oystercatchers and common
ringed plovers Charadrius hiaticula. This coastline is a popular tourist destination,
particularly in the summer when several species of wader, gulls and terns are attempting
to breed. During the summer, on three days of peak human beach use (hot sunny days)
the distribution and numbers of people were plotted (via video from a light aircraft).
Taking into account habitat factors, results indicate that human disturbance on these
beaches influence territory choice of both oystercatcher and ringed plover which select
territories where human disturbance is relatively low, both at the scale of the whole
Norfolk and Suffolk coast, and within areas of this coastline.
Verlust et al. (2001) undertook two short experiments to quantify effects of human
disturbance on foraging and parental care of oystercatchers on Schiermonnikoog, an island
in the Dutch Waddensea. In the first experiment conducted over three days, incubating
pairs were disturbed on their mudflat feeding territory. The first and third days acted as
controls (no disturbance), whilst on the second day, use of the feeding territory was
prevented from 2 h before until 1 h after low tide by approaching feeding birds.
Disturbance significantly reduced the proportion of time that eggs were incubated. In the
second experiment, foraging adults with chicks were disturbed by two observers seated on
the mudflat at different distances from the edge of the saltmarsh where the chicks were
present. Total food collected by adults was independent of disturbance but a smaller
proportion was allocated to chicks as disturbance levels increased. Both experiments
indicate that human disturbance of foraging adult oystercatchers reduces the amount of
parental care, which may in turn affect reproductive success.

57
African oystercatcher Haematopus moquini
Hockey (1997) considered that recreational disturbance may contribute to population
declines of this near-threatened species, endemic to Namibia and South Africa. African
oystercatchers tend to nest on beaches (many now popular with people) where nests are
vulnerable to destruction through trampling and being run-over by vehicles, and eggs and
chicks may be predated by domestic dogs. Disturbance can also result in drowning of
chicks and loss of adult foraging time (Lambeck et al. 1996). Summers and Cooper (1977)
also recorded that egg predation by gulls occurred when oystercatchers left there eggs
unattended as a result of human disturbance. Hockey (1983) in a study of 55 oystercatcher
pairs breeding on Marcus Island (South Africa), found that egg losses were high, primarily
due to predation by kelp gulls Larus dominicanus. As observed in earlier studies, predation
was exacerbated by human disturbance which forced incubating birds from their eggs.
It was thought that disturbance might also result in adults having insufficient time to satisfy
their own and their offspring‟s food requirements. To this end, Leseberg et al. (2000)
undertook a study to test if affects of foraging disturbance might vary regionally in
response to variation in foraging conditions. Foraging times of adult oystercatchers were
recorded at four protected areas (spanning 750 km of the South African coast) that
experienced little or no human disturbance. Time spent foraging per day increased from
west to east, paralleling a west–east decrease in intertidal primary productivity and biomass
of grazing invertebrates (potential oystercatcher prey). There was also a west–east decrease
in oystercatcher density. At two sites (De Hoop and Goukamma) where food intake rates
are relatively low, oystercatchers regularly experience difficulties rearing two chicks under
undisturbed conditions (only 19% and 8% of pairs rearing two chicks). It is thought
therefore, that their ability to rear even a single chick could be compromised by even fairly
low disturbance levels. At both sites, oystercatcher numbers have increased in recent years
(up by 30% at De Hoop over 14 years, and 57% at Goukamma over nine years)
corresponding to a reduction in human disturbance; at De Hoop in 1986 angling, bait-
collecting and use off-road vehicles on beaches was stopped, and at Goukamma in 1990,
bait-collecting, night-time shore angling and use of vehicles associated with commercial
oyster harvesting was halted. Fledging success was also noted by Hockey (2002) to be
generally higher in such protected areas.
Jeffery and Scott (2005) studied the breeding success of African oystercatcher on a 12 km
section of coast west of Cape Agulhas (South Africa) from 1978 to 2002. An average of
15.9 (± 4.5) pairs bred per year with a significant increase over the study period despite a
decline in nesting success, this decline attributed largely to increased use of off-road
vehicles on beaches (and perhaps also the result of a natural cycle). Of relevance to this
review is the behaviour of birds as a vehicle approached a nest, stopped and people
alighted. Oystercatcher pairs were observed to be little affected by a vehicle (often not
moving from a nest even if passed within 2 m) unless it stopped and people stepped out.
Some pairs moved higher up the beach and re-nested, apparently to avoid more disturbed
areas. There were few observations of direct impacts due to access on foot, but at least two
nests were trampled. The greater ownership of off-road vehicles has led to greater ease of
access to remote beaches, and this, along with associated people walking or undertaking
other recreational activities may be impacting breeding success. Tourism and coastal

58
development are growing which could have long-term implications - high adult
survivorship makes census data alone a poor predictor of future population trends, with
productivity probably declining due to increased recreational disturbance (Hockey 2002).
Common ringed plover Charadrius hiaticula
Tratalos et al. (in prep.) undertook a survey of the Norfolk and Suffolk coastline
(southeast England) of beach-nesting common ringed plover and Eurasian oystercatcher
(see Eurasian oystercatcher account, above, for further details). Results indicate that
human disturbance influences territory choice, both species establishing territories where
disturbance is relatively low, although habitat features were also critical For ringed
plovers this effect was shown to occur at small scales, with a negative relationship
between numbers of visitors and presence of plover territories even when sections not
containing or adjacent to an occupied section were excluded from analyses.
Liley (1999) undertook a 3-year study investigated the consequences of human
disturbance for ringed plover populations along the west coast of Norfolk. Human
disturbance, largely attributable to holiday makers, was especially concentrated around
car parks (points of beach access) over two weekends in May (extended weekend holiday
periods), and during July and August (school holidays) at the end of the plover breeding
season. Disturbance came mostly from walkers (with or without dogs), sun-bathers and
occasional picnickers, anglers and bait-diggers. Highly disturbed sections of beach were
avoided by most nesting pairs (with the exception of those with no prior experience of
breeding on the site) despite presence of otherwise suitable habitat. Where nesting
occurred, density of territories and nests was less along more disturbed sections. Of all
nests found, 8.5% were lost due to people, mostly (83.5%) though accidental trampling of
the well camouflaged eggs, with a higher proportion of losses occurring closer to
footpaths. An experiment with dummy nests revealed that 23% were lost to trampling,
with more trampled where the density of people was higher. Disturbance did not affect
incubation length, proportion of nests that hatched, or chicks fledged, although only low
disturbance areas were considered. Chick foraging time was reduced in areas with more
people but this had no effect on growth or survival to fledging, but whether this had any
other impacts e.g. on chick fledging weight and subsequent longer term survival, is not
known. A model was constructed that predicted that if human activity was restricted (e.g.
through fencing of sections of beach with nests) then the ringed plover breeding
population size would increase by about 8%, whilst if people were absent altogether the
population would increase by around 85%.
In order to gain an insight into the effects of human disturbance, Rooney and Eve (1993)
monitored 10 ringed plover nests on the north Norfolk coast over three days (the May
Bank Holiday period) on a beach which traditionally experiences high numbers of
tourists. When a person approached to within 100 m most plovers reacted by leaving the
nest. For long periods there were constantly people within 100 m of all 10 nests. If people
sat quietly within 50 m of a nest, especially if partly concealed by sand dunes, an adult
would return to incubate. However, most visitors comprised family groups, and quiet
recreational activity, giving plovers the opportunity to recommence incubation, was rare.

59
Pienkowski (1984) undertook a study of breeding ringed plovers at Lindisfarne, northeast
England. Clutch survival to hatching was highly correlated with disturbance at three
study sites over two breeding seasons. Nest survival averaged 50% in an area with around
five human visitors/day, 27% in an area with up to 50/day, but only 1.7% in the area
experiencing over 100/day. Unintentional disturbance by visitors and their dogs (see 5.4
Domestic dogs and disturbance) was considered more serious than direct loss (e.g.
through trampling) as incubating birds normally ran from nests when approached, giving
opportunities for carrion crows Corvus corone and other avian predators, watching for
plover movement, to locate and predate the eggs. It was noted that increased movement
to and from nests by ringed plovers due to disturbance, left tracks on sandy substrate
leading to the nest scrape, and also possibly scent trails that mammalian predators (e.g.
red fox Vulpes vulpes) might exploit.
Piping plover Charadrius melodus
There have been many studies looking at the effects of human disturbance on piping
plover, a rare and declining North American wader. Concentrations of people appear to
deter them from using otherwise suitable habitat. In Massachusetts, Hoopes (1993) found
95% of piping plovers (n = 209) occurred in areas that contained less than one person per
8,100 m² of beach. Elias-Gerken (1994) found that on Jones Beach Island, New York,
piping plovers nested on stretches of beach with less pedestrian disturbance compared to
where no plovers nested. On nearby Rhode Island, sections of beach were colonized by
piping plovers within two seasons of their closure to heavy pedestrian recreation (Blair &
Kurth, in Anon. 1996, U.S. Fish and Wildlife Services).
Lauro and Tanacredi (2002) investigated reasons for piping plover nest and chick loss at
Breezy Point, New York, over five breeding seasons (1992-1996). The focus was to
determine predatory pressures on breeding birds, as predation was known to be a serious
problem at this site. The reasons for egg loss were often unknown (68%) but those
identified were tidal flooding (2%), human disturbance (4%) and predation (26%)
primarily by crows Corvus spp. and gulls Larus spp. The human disturbance data is
unfortunately difficult to interpret; all 20 cases of egg loss attributed to people occurred
in one breeding season (1994) but the actual causes (other than „human‟) are not stated.
National Parks staff managed the beaches during the study period, fencing of some
stretches and imposing restrictions on bather and vehicle access, but other forms of
potential human disturbance are not described.
Burger et al. (1995) (after Burger 1987, 1990, 1991) constructed a model to illustrate the
effects of people on foraging activity of breeding piping plovers and parental care using
data from three beaches on the New Jersey coast (USA). Observations showed that as the
number of people within 10 m of a foraging adult plover increased, the time spent feeding
decreased whilst „alertness‟ increased; they also avoided sections of beach where people
were present. The model suggests that with increased human presence adults have
difficulty in finding sufficient food as foraging is disrupted. This in turn reduces the time
for egg or chick defence. Further, when a person approaches an adult piping plover with
young, they perform distraction displays whilst the chicks run and hide. As a result, if the
brood is more than a single chick, parents have difficulty keeping their offspring together,

60
bringing with it associated problems. The authors suggest that because of the detrimental
effects on productivity, closure of sections of beach to exclude people and their dogs
during the breeding season may be the only option to enhance breeding success.
Flemming et al. (1988) undertook observations of piping plover on breeding beaches in
Nova Scotia (Canada) to assess responses to human disturbance. The study population was
66-71 pairs in 1983, declining to 48-54 pairs by 1987. Since piping plovers are relatively
long-lived and site faithful, the authors suggest that continual low fledging success was
probably responsible for this population decline, rather than birds simply moving to other
areas to breed. The low fledging success was considered due, in part at least, to human
disturbance. Levels of disturbance were quantified over five years (1979-1983) by
recording positions of people, their footprints and vehicle tracks. It was found that parents
brooded chicks less when disturbance was higher, and responded to approaching humans at
a higher level than other potential predator and non-predatory species. Increased
disturbance led to fewer chicks surviving to fledging (17 days old). The number of chicks
surviving/nest attempt was 1.8 young/pair in areas of low disturbance compared with 0.5 in
areas of high disturbance. When people approached closer than around 160 m, chicks spent
less time feeding, and when they did feed it was at a lower rate (5.7 pecks/min when
disturbed, 12.5 pecks/min when undisturbed). Cairns (1982) reported that plover chicks in
Nova Scotia that failed to achieve 60% of their normal body weight by day 12 were
unlikely to survive to fledging, and Loegering and Fraser (1995) demonstrated that
reduction in foraging time and foraging efficiency may be critical for chick survival.
Goldin and Regosin (1998) studied piping plovers at Goosewing Beach, Rhode Island
during 1993 and 1994. Broods with access to salt-pond mudflats experienced higher
fledging success (3.0 fledglings/brood) than those limited to ocean beachfront habitat (1.4
fledglings/brood). This difference may have been due to the mudflats affording better
foraging opportunities. However, broods on the mudflats spent less time responding to
human disturbance (1.6%) than chicks on the more disturbed beachfront (17%) which also
impacted on available foraging time. Whether the difference in time spent feeding between
the mudflats (78%) and beachfront (51%) habitats affected fledging success is unknown.
Recreational use is often cited as a probable factor in preventing this species from nesting
(e.g. Bowles et al. 1981, Flemming et al. 1988) and preservation of nesting habitat and
protection from human disturbance during the breeding season are considered important
to maintain and re-establish piping plover populations.
Kentish plover Charadrius alexandrinus
Schulz and Stock (1993) studied a 90 ha area of beach and dunes used by breeding
Kentish plovers in Schleswig-Holstein, northern Germany. The area was heavily used by
people, apart from a 12 ha protected area within a National Park. Over one breeding
season (1990) plover nests were monitored and habitat variables recorded. The number
and position of people mapped on 50 of the busiest days throughout the breeding season
was used as a measure of disturbance intensity. The areas of habitat considered to be the
most suitable plover breeding habitat were those most heavily used by people; as a
consequence large areas were not settled and most nests were situated away from such
areas. In this breeding season, 120 plover pairs made 178 breeding attempts. Of the 130

61
nests located the outcome of 101 was known; 66 were successful, 35 failed. In areas with
high recreational disturbance clutch loss (36%) was much higher than areas of low
disturbance i.e. in a protected zone with restricted access (10%). In the study area,
walkers mostly followed the high tide line and thus rarely approached nesting areas, but
may have disrupted foraging activity. Resting people (e.g. picnickers and sunbathers)
tended to cause more disturbance as they were located in the proximity of the nests higher
up the beach. Nesting success was also influenced by vegetation cover in areas heavily
used by tourists, with a much higher rate of failure (50%) in sparsely vegetated areas
compared with those nests in dense vegetation (14%). The authors suggest that as more
nests in open areas failed, this indicated that aerial avian predators were likely to be the
main cause of losses, with the increased human disturbance making it easier for predators
to locate nests.
Snowy plover Charadrius nivosus
Ruhlen et al. (2003) examined the rate of snowy plover chick loss at different levels of
recreational disturbance on beaches in Point Reyes National Seashore, California, USA.
During weekends and holidays (chick exposure days: 319 weekend/holiday days vs. 505
weekdays in 1999; 216 weekend/holiday days vs. 364 weekdays in 2000) when human
beach visitation increased, chick loss was 72% greater than expected in 1999 and 69%
greater than expected in 2000. Over the two years, average chick loss was 65% during
weekends and holidays but only 35% on weekdays. This suggests that increased human
visitation negatively affected chick survival, although how this did so was not determined.
Lafferty et al. (2006) looked at the effect of reducing human access on the beach at Coal
Oil Point Reserve (California) where snowy plovers had bred up to the late 1960s, but
ceased to do so (apart from occasional nest attempt) when it was opened for public
recreation. In June 2001 a 280 m stretch of dry sand was roped off (with people still
allowed to walk past on wet sand close to the water‟s edge and requested to keep dogs on a
lead) and a single pair successfully bred. The roped off area was increased to 400 m in
length in 2002, and expanded further in 2003-2004 to protect nests outside the 400 m
boundary. In response, disturbance incidences during the breeding season (recorded as a
run/move or flight in response to a person or dog) fell by over 50%. Dummy nests in 2002
showed that the probability of egg loss to trampling was 8.1% outside the roped area and
0% within it. Numbers of breeding pairs, nests, eggs and young fledged increased each year
following protection (five pairs fledging 14 young in 2002, rising to 26 pairs fledging 74
young in 2004). The initiation of breeding following protection strongly implies that a
reduction in human and dog disturbance encouraged snowy plovers to return and breed.
New Zealand (dotterel) plover Charadrius obscurus
Lord et al. (2001) looked at the affect of deliberate human approaches to 15 pairs of
beach nesting New Zealand plover (North Island subspecies C. o. aquilonius) during one
breeding season. Three different approaches were undertaken: walking, walking with a
dog on a lead, and jogging. Of these, walking with a dog was found to cause most
disruption, with incubating birds flushing significantly earlier and remaining off the nest
for significantly longer (see also 5.4 Domestic dogs and disturbance). There were
indications of some habituation to human activity, with birds nesting on high-use beaches

62
consistently showing a tendency to allow a closer approach before flushing and staying
off their nests for shorter periods than birds nesting on remote beaches. Chicks also spent
less time foraging when people were nearby, the assumption being that this could affect
survival if they were unable to compensate for lost feeding time, and if they failed to
achieve a suitable body weight this could prevent successful fledging, as supported by
several studies of other shorebirds e.g. piping plover (Cairns 1982).
Hooded (plover) dotterel Thinornis rubricollis
Dowling and Weston (1999) monitored the population of hooded dotterels over seven
breeding seasons along the Mornington Peninsula National Park coast, Victoria, southeast
Australia. The area is heavily used by people, activities on the beaches including
swimming, surfing, sunbathing, fishing, jogging and walking (including with dogs on a
lead in permitted areas, although often dog walkers ignored the restriction and let dogs
run free). A total of 171 nests were located and of these, by far the main cause of
hatching failure was loss of clutches due to trampling by people with 53 (30%) of nests
lost in this way. The other causes of known egg loss were red fox predation, flooding, and
abandonment (just under 2% of nests each), whilst 40% of nests hatched successfully.
The highest proportion of nests trampled were on the beach (51%) where human activity
was concentrated, but trampling was also high in dunes behind beaches (21%) where
„dune boarding‟ was becoming increasingly common. Of 128 chicks monitored, 27%
fledged but the causes of mortality although unknown, was partly attributed to dogs (see
also 5.4. Domestic dogs and disturbance).
Weston and Elgar (2005) examined the causes and consequences of disturbance to
hooded dotterel chicks from Johanna Beach to Oberon‟s Bay on the coast of Victoria.
The main source of disturbance was from humans (81%), mostly people walking along
the beach without a dog (57%) sometimes with a dog on a lead (2%) or off lead (15%),
and also joggers (7%). In response to human approach, brood-rearing adults usually led
their chicks away and either watched from distance whilst the chicks lay hidden (on the
beach or in the fore dunes), or used aggressive or distraction displays. It was thought that
adult brood defence might be compromised by human disturbance but there were no
observations of any incidences of predation by avian predators (the most abundant
potential predators present) during disturbance events. The number of minutes a chick
spent hiding per hour was higher (30 min) during relatively disturbed days (weekends and
holidays) compared with relatively undisturbed days during the week (22.5 min). The
time chicks spent foraging per hour was also lower on relatively disturbed days (12.5
min) compared to relatively undisturbed ones (19.4 min). There was also a tendency for
broods to forage along lower parts of the shore (potentially with greatest food
availability) when undisturbed. It was considered that as well as impeding food uptake
due to interruption of foraging, the run and hide response of chicks was also probably
energetically costly. Adults brooding chicks exhibited a 31% reduction in brooding time
in response to human activity; some chicks went unbrooded due to disturbance for up to
almost 5 h and were exposed to temperatures of 10 to 46˚C, whether this caused thermal
stress is not known. At this locality disturbance from humans was more frequent than
that from natural causes. No direct link was established between human disturbance and

63
reduced reproductive success, but the mechanisms by which this could come about are
demonstrated.
Least tern Sterna antillarum
Burger et al. (1995) evaluated the effects of ecotourism on several species of birds in
coastal New Jersey, USA. At colonies of least tern they assessed breeding success
relative to three types of human disturbance: primarily ecotourists; primarily other types
of disturbance (e.g. sunbathers, joggers, walkers with dogs, anglers); and few ecotourists
and few other disturbances. Overall, fewer birds nested and fledged fewer young per pair
at colonies where ecotourists were prevalent compared to other colonies. However, it is
difficult to assess the real affects of human disturbance at the respective study colonies as
disturbance levels were not well quantified e.g. colonies visited by birdwatchers had
more visitors generally than other beaches and were visited throughout the breeding
season but whether with increased numbers of birdwatchers breeding success declined
was not determined. Potential confounding environmental factors need also to be taken
into account, e.g. colony location and natural vulnerability to predation.
Bridled tern Onychoprion anaethetus
Gyuris (2004) examined the impact of recreational visits on breeding sooty terns at
Rocky Islets National Park (Great Barrier Reef World Heritage Area), Queensland,
Australia. Two levels of human disturbance were implemented at five sites over three
breeding seasons. In the first year, there was no disturbance other than minimal routine
monitoring and this was used as a general control. In the subsequent two years,
experimental disturbance at three sites commenced when 50 nests had been found.
Disturbance regimes were designed to simulate low to moderate levels of visitation
experienced on many Great Barrier Reef islands. Three variables were examined:
hatching success; chick weight; and bill length at 12-13 and 21-22 days (fledging age)
old. Hatching success was higher and chick weights significantly heavier at 12-13 days at
sites exposed to greater levels of disturbance. The author suggests that these results
indicate that early development of chicks may be adversely affected by disturbance but
that such affects may be ameliorated by habituation to human intrusion into nesting areas.
Habituation is a reasoned assumption as bridled terns use the same nest sites each year
thus the birds in this study were repeatedly exposed to human presence. That they may
have become habituated to some degree is backed by other observations. For example, in
a study of common terns Sterna hirundo, Nisbet (2000) observed that the birds exhibited
pronounced signs of tolerance by the middle of the second season of exposure to
researcher disturbances.
Heermann’s gull Larus heermanni
Anderson and Keith (1980) assessed the effect of human disturbance on productivity of
Heermann‟s gulls in Baja California, Mexico. Censuses in 1974 at two colonies
representing three disturbance intensities indicated that the number of young (expressed
as young/100 full-breeding adults) was detrimentally affected by disturbance (no
disturbance 17.7 young; moderate disturbance 13.6 young; heavy disturbance 4.5 young).
Human intrusion induced massive „confusion‟ within a colony with territorial

64
displacement of adults and young resulting in egg destruction and death of young caused
by neighbouring gulls.
American herring gull Larus smithsonianus
Hunt (1972) looked at herring gull reproductive success on four islands in Penobscot
Bay, Maine, northeast USA. Disturbance was measured on the basis of the number of old
fireplaces, beer cans and picnic groups encountered during visits. Hatching success was
lower in gull colonies frequented by more picnickers, regardless of proximity to prime
foraging sites. Hatching success averaged 22% over two years at the two disturbed
colonies and 48.5% at the two undisturbed colonies. It is suspected that when the adults
were flushed, eggs were left exposed and overheated, causing embryo death. Unattended
eggs were also predated by other gulls. However, chick rearing success was similar, with
40.5 and 35.5% successfully fledged at the disturbed and undisturbed colonies
respectively.
CLIFFS
Common guillemot Uria aalge
Beale and Monaghan (2004) developed a model of perceived predation risk to help
understand the effects of human disturbance on two cliff-nesting birds. The model
predictions were tested using field data on nesting success of common guillemot (and
black-legged kittiwake Rissa tridactyla; see below) at St. Abbs Head National Nature
Reserve (Scotland) during the 2002 breeding season. On the cliffs 241 nests were
selected and observed daily. Lay date to within two days, hatching and fledging success,
and the number of people passing by were recorded. Manipulations of people consisted of
allowing access to usually inaccessible areas (e.g. fenced off zones) or increasing
numbers at viewpoints, assisted by volunteers for this purpose. Nest success was 70%
with most failures (62%) during the egg stage. It was correlated with both people load
(i.e. average index of people min/h divided by distance from the two nearest viewpoints)
and average distance. Overall, the presence of people had a strong negative affect on
nesting success. The model suggests that increasing visitor numbers by only 8.5%
resulted in a 13% increase in failure rate, while halving visitor levels resulted in a nesting
success of 87%. When people load was kept constant, nesting success was negatively
correlated with the average distance people were from nests.
Schauer and Murphy (1996) found that when people approached nesting guillemots,
accidental dislodgement of eggs occurred as adults were flushed from rock ledges, and
predation of eggs, mainly by glaucous gull Larus hyperboreus, occurred when adults left
eggs unattended when disturbed. Most predation appeared to occur early in the breeding
season when human disturbance was highest and adult guillemots seemed most likely to
temporarily abandon their egg.
Black-legged kittiwake Rissa tridactyla
In addition to guillemots Beale & Monaghan (2004) looked at the effect of human
disturbance on kittiwake breeding success. A total of 106 nests were selected (see
guillemot account, above, for disturbance methods) of which 42.5% successfully fledged

65
at least one chick, with most failures (59%) occurring during the chick-rearing (as
opposed to incubation) period. Overall, nesting success was strongly related to the
presence of people. The model suggests that increasing visitor numbers by 8.5% resulted
in a decline in nesting success to 29% (a 22% increase in failure rate) while halving
visitor levels resulted in a nesting success of 96%. When people load was kept constant,
the average number of people minutes per hour was positively correlated with nesting
success, whilst the distance these people were from the nests was negatively correlated.
However, the model does not take into account habituation to human disturbance which
might be expected to occur in this species; some kittiwake colonies are remarkably
tolerant of disturbance with breeding success appears little affected by it. For example,
one long term study on the island of Røst (Lofoten Islands), Norway (pers. comm. Tycho
Anker Neilson & Tomas Aarvark 2006) involves a population of kittiwakes nesting on
buildings. People walk by many occupied nests to within 1-10 m during everyday
activities. During the course of occasional additional disturbance caused by research
activities (e.g. to ring birds), displaced adults or those caught and temporarily removed
for a few minutes rapidly return to nests upon release (pers.obs.) and breeding success
appears unaffected. Sandvik and Barret (2001) found that despite extensive researcher
disturbance of nesting kittiwakes (again in Norway) any effects were small, although
adult nest attendance decreased and daily chick loss rates were slightly higher. Overall
chick survival until day 18 (around fledging) was significantly lower in the first than in
the second year of the study. The authors suggest that a reduction in herring gull Larus
argentatus predation as a consequence of disturbance was responsible (gulls nesting
nearby were more susceptible to the effect of disturbance than the kittiwakes themselves);
kittiwake habituation to disturbance may also have been a factor.
Peregrine falcon Falco peregrinus
Brambilla et al. (2004) aimed to assess the significance of rock climbing-induced
disturbance and/or raven Corvus corax occurrence on breeding productivity of cliff-
nesting peregrines in the provinces of Varese Como and Lecco, northern Italy, and
Canton Ticino in southern Switzerland. Breeding success was recorded over one breeding
season in 2002 at known breeding sites. Pairs (14) that nested on cliffs undisturbed by
climbers and in the absence of ravens had the highest breeding success, fledging on
average two offspring per territory. Conversely, on five cliffs where both climbers and
ravens were present no young were fledged, this being tentatively attributed to raven
predation of eggs/chicks due to attending peregrines being scared away by the presence
of climbers. There were only two peregrine pairs in this study found nesting on cliffs
frequented by climbers but with ravens absent, one of which fledged young; with such a
small sample size it is not possible to draw any firm conclusions with regards the effect
of climbers on peregrine reproductive success.
WETLANDS
Western marsh harrier Circus aeruginosus
Fernández and Azkona (1993) studied the effects of human disturbance on parental care
by marsh harriers over one breeding season at Dos Reinos Lake, Ebro Valley, Spain.

66
They assessed changes in harrier reproductive activities and nestling nutritional condition
in relation to low-level human disturbance. Six pairs (of 11) in the study area were
observed daily and their behaviour compared in disturbed and undisturbed periods. The
number of food items delivered by the male to the female, and the time spent by parents
in the nesting area and on the nest itself, decreased during disturbed periods especially
during incubation, whilst behaviours considered to be related to stress (alarm calls, chases
against other birds intruding on the territory, and time spent flying) all increased 20-fold.
Compared to the five pairs not subject to disturbance, productivity of the disturbed pairs
(i.e. chicks fledged per pair) was not affected but their nestlings exhibited higher levels of
blood urea (an indication of lower nutritional status). Of the 25 eggs laid by the six
disturbed pairs, 16 chicks were successfully fledged (64%), whereas of the 24 eggs laid
by the undisturbed pairs, likewise 16 chicks fledged (67%). The authors hypothesize
that the minor human disturbances might reduce future breeding condition through
increased expenditure of energy and time on non-reproductive activities, and reduced
nestling condition may potentially affect subsequent survival after fledging.
Penny Anderson Associates (2003), collated observations during closure of parts of the
countryside in the UK during the 2001 foot and mouth disease epidemic. Changes in
marsh harrier nesting patterns were attributed to the lack of people and their dogs, with
harriers nesting much closer to paths than usually recorded in several nature reserves in
eastern England during the closure period.
HEATHS and LOWLAND GRASSLAND
Eurasian stone-curlew Burhinus oedicnemus
Taylor (2007) undertook a study of the effects of human disturbance on breeding stone-
curlews Burhinus oedicnemus in Wessex, southern England. Recreational disturbance in
the vicinity of breeding plots (blocks of farmland managed to provide suitable stone-
curlew nesting habitat) during the early spring settlement period had a negative effect on
plot occupancy. It was predicted that under current disturbance levels, removal of all
recreational disturbance would result in an 11% increase in plot occupancy (equivalent to
six extra plots occupied in the study area). Dog walkers were by far the most important
disturbance factor, their removal alone resulting in a 10% increase in plot occupancy
probability. Investigating the effects of human disturbance on breeding success over two
breeding seasons, it was found that chicks grew more slowly on sites with disturbance but
this had no influence on survival to fledging. No other significant effects were observed,
suggesting that there are either few adverse impacts of disturbance on breeding success,
or that stone-curlews selected to nest in less disturbed plots where the impact of low level
disturbance on breeding success is not manifested. Evidence suggests that breeding pairs
do in fact, select less disturbed areas. Observations of colour ringed adults after their
arrival in spring, but prior to breeding, showed that 40% of pairs moved between sites
before settling to nest. Pairs often moved if disturbance at the first potential nesting site
was high, moreover, for pairs that moved, the second site chosen was significantly less
disturbed. Pairs that moved bred, on average, a week later than those which did not
move. This delay is considered likely to reduce the chance of producing a second brood,
or re-laying in the event of clutch or brood failure.

67
European nightjar Caprimulgus europaeus
Liley and Clarke (2002, 2003) undertook an analysis of nightjar breeding densities on
Dorset heaths in southern England. They found that there was no difference between the
location of the centre of a nightjar territory and random points with respect to distance to
roads or a heathland edge, but territory centres were significantly further away from the
nearest built-up area (Liley & Clarke 2002). They went on to integrate existing data sets
of factors potentially influencing nightjar numbers on 36 heathlands in Dorset. Although
no observations of human disturbance were incorporated, surrogate disturbance measures,
including the amount of developed land at different distances from the heath and the
number of buildings, were used. These were highly correlated and showed a strong
negative relationship with the density of nightjars present on a heathland patch, regardless
of its size. The amount of surrounding woodland (a preferred nightjar foraging habitat)
within 500 m of the edge of a heath was positively correlated with nightjar numbers and
significantly improved nightjar density predictions. The study demonstrates that nightjar
numbers on a heathland are influenced by surrounding land use, with sites surrounded by
more development supporting lower nightjar densities, the effect of urban development is
thus more than just habitat loss. The authors suggest that this is at least partly due to
human presence on heaths, as it has been shown that people living close to heaths in
Dorset regularly visit them, and that high levels of recreational use e.g. dog walking, are
evident on some. They further suggest that where open access to heathlands is proposed
in light of CRoW, access management to avoid deleterious impacts to nightjars need to be
considered.
Murison (2002) looked at the impact of human disturbance (mostly dog walkers) on
nightjar breeding success, also on Dorset heaths. In 2002, nightjar territories on 10 sites
were mapped, as many nests as possible were located and monitored to fledging. Of the
47 nests found, 19 (40%) were successful and 28 (60%) failed (24 at the egg stage). Of
those that failed, 93% were lost due to predation, mainly by corvids (63%), with nine
(37%) attributed to mammals. There was a negative relationship between both density of
nightjar territories and the proportion of successful nests (i.e. those producing at least one
fledged young) on sites, with the number of buildings within 500 m of the site
boundaries. Paths were categorised as low, medium or high use. Nests were more likely
to be predated closer to paths, and the greater the length of high/medium use paths within
500 m of a nest, the poorer the breeding success. The results hint that human disturbance
might increase predation, perhaps by flushing of incubating or brooding adults thus
bringing to the attention of, and exposing them to predators. Although not quantified,
dogs off leads (from anecdotal evidence from this and other studies) may flush adults and
also occasionally kill chicks, but conversely dogs have also been shown to flush adults
and approach eggs or chicks and leave then unharmed.
Woodfield and Langston (2004), looked at nightjar nesting success in relation to access
levels on four heaths surrounded by developed land, all receiving high recreational use.
During the 2003 breeding season, nests were located and monitored, eight by using video
cameras. Ten (34%) of the 29 nests found, all at the egg stage, failed. Of the 19 that were
successful, 32 young were fledged. Human visitation rates were recorded by undertaking

68
transect walks across the sites at hourly intervals during the day throughout the breeding
season. Additional counts were made in the proximity of nests during peak visitor
periods. The nest cameras recorded 12 flushing events of a sitting nightjar, one being
flushed by a dog once whilst incubating, and again whilst brooding chicks, but the young
fledged successfully. One flushing incident led to predation of the eggs by a carrion crow
Corvus corone. It was calculated that the nightjars on these highly disturbed heaths had
on average, a 12% chance of being flushed each day. All flushing events (the cause of
which was not always known) were assumed to be caused by disturbance as nightjars do
not leave the nest during the day otherwise. Similar to the results of Murison (2002),
nesting success decreased with footpath proximity, and also decreasing vegetation cover
around nests. However, due to the small sample sizes, none of these findings were
statistically significant. Results from these latter two studies suggest that nightjars (which
lay clearly visible white eggs) suffer greatest nest failure (36-86%) at the egg stage. The
eggs are obvious if the camouflaged adult is flushed, and circumstantial and direct
evidence points to predation upon flushing as being a problem.
Woodlark Lullula arborea
Mallord (2005) undertook a three year study investigating the consequences of human
disturbance, urbanisation and habitat fragmentation for a woodlark population on heaths
in Dorset, England. Across heaths, woodlark density per hectare of suitable habitat was
lower on sites with higher levels of human disturbance (mostly walkers, many with dogs
either on or off lead). Of heaths with recreational access, the probability of suitable
habitat being occupied was lower in areas with greater disturbance - at around only eight
disturbances an hour, occupation probability fell below 50%. A survey across 12 heaths
in 2002 and 16 in 2003 showed that at low disturbance (<0.01 people/survey/ha) the
density of woodlark pairs was around 0.6 pairs/ha of suitable habitat, whilst at the highest
disturbance levels recorded (>0.1 people/survey/ha) woodlark densities fell to around 0.1-
0.2 pairs/ha. However, woodlarks nesting on more disturbed heaths fledged more chicks
per pair due to a greater density-dependent reproductive success throughout the breeding
cycle, including recruitment into the local breeding population. This density dependent
breeding success partially balanced the negative effects of disturbance, but it was
calculated that there was a 34% reduction in productivity to that predicted in the absence
of disturbance. A model was constructed that predicted that the impact on the woodlark
population depended both on numbers of people and their distribution on the heaths.
Under access arrangements at the time of the study (i.e. most people using footpaths and
keeping to fairly defined areas), the model suggested that a doubling of visitors had little
effect, whilst the same number of people distributed evenly across all sites (a theoretical
scenario) led to a major negative impact on the population. This latter prediction
however, exemplifies the importance of site management and perhaps restriction of
access to some areas during at least the breeding season, and an obligation to keep dogs
on a lead during this period for the benefit of ground nesting birds in general.
Liley and Clarke (2002) in a study of the impact of urban development around heaths,
found no apparent effects of more surrounding developed land on woodlark territory
density (used as a surrogate for human disturbance), but like Mallord (2005), showed that

69
there were fewer territories on sites with open access (higher disturbance area) compared
with ones that were closed to the general public (lower disturbance areas).
Taylor (2002) conducted a nest predation experiment on a selection of Dorset heaths over
one breeding season using clay eggs in artificial woodlark nests placed in typical
woodlark habitat (but at higher densities than would naturally occur). There were three
main significant trends recorded: corvid numbers increased at higher levels of human
disturbance; nest predation increased as predator numbers increased; and predation
increased at higher levels of human disturbance. The predation rate of the artificial nests
was 69%, and where a predator could be identified 53% were corvids and 26% foxes
V.vulpes. Predation was also higher in areas with less vegetation cover and shorter
vegetation. However, despite being undertaken on the same study heaths as Mallord
(2005), these predation rates bore no similarity to that found for real woodlark nests.
Inferences that nest predation increases with human disturbance drawn solely from such
artificial egg predation experiments should therefore be viewed with caution unless data
on predation rates of real nests is also available.
Western meadowlark Sturnella neglecta; Vesper sparrow Pooecetes gramineus;
Grasshopper sparrow Ammodramus savannarum
Miller et al. (1998) investigated the influence of recreational trails on breeding bird
communities in forest and mixed-grass prairies in Boulder County, Colorado, USA over
two breeding seasons. The area comprises agricultural land and areas reserved for
recreation e.g. hiking, exercising pets, jogging, mountain biking, horse riding and wildlife
watching. The intensity of recreational use is extremely high. In the grassland areas, nests
of ground-nesting birds were located from the edge of trails out to 200 m, ensuring equal
search effort at all distances (by dragging a rope across the ground). No nest
abandonment was caused by this search method. Number and distance of nests from trails
was monitored for 5 weeks in 1994 and 7 weeks in 1995. Control transects in grassland
away from trails were also established, where three ground-nesting grassland species,
western meadowlark, vesper sparrow and grasshopper sparrow, were found to be
significantly more abundant than along trail transects. Western meadowlark and
grasshopper sparrow were less likely to nest near trails. Nest predation of all three species
was greater closer to trails. Probability that a nest in the grassland would survive one day
(n = 163 nests; 1,954 nest days) was related to distance from trails; the further the
distance from a trail, the higher the probability of survival. Overall, the results indicate
that bird composition and abundance were altered adjacent to trails with some grassland
specialists occurring in and nesting at lower densities near trails, and nest predation rates
being higher closer to trails.
Dark-eyed junco Junco hyemalis
Riffel et al. (1996) over five breeding seasons (1989-1993) experimentally assessed
whether repeated human intrusions resulted in cumulative impacts on birds in the
Medicine Bow National Forest, Wyoming, USA. Repeated intrusions were made into 1
ha plots by a lone walker and the number and species of birds in these were compared
with undisturbed control plots. Intrusions lasted 1-2 h each week over 10 weeks and were
undertaken at two intensities: 1 or 2 days/week. Disturbance plots were radially walked

70
and any bird observed was approached directly. On approach birds were flushed from
resting, feeding, singing or nesting areas. Declines in avian richness and abundance
were tested for at the community, nesting guild (cavity nester; open-nester <2 m above or
actually nesting on ground; open-nester nesting at >2 m above the ground) and species
level. The average number of individuals on a site during a census during a given year
was analysed for four common passerines, one of these being dark-eyed junco, a ground-
nester. Relative richness and abundance were the only metrics to exhibit declines between
years over the five study years. These declines however, were not cumulative and
significant declines in abundance were not evident. Fourteen species fell into the
understorey nesting guild, of which nine habitually nest on the ground or very close to it.
No decreasing trends were evident in the mean percentage of controls for richness of
migrant or resident understorey-nesting species. The authors suggest that cumulative
declines were not apparent as individuals displaced one year may have been replaced in
subsequent years, and some individuals may have become habituated to the disturbances.
Therefore in this particular locality for those bird communities studied, they propose that
management should focus on preclusion or amelioration of short-term disturbance
impacts.
MOORLAND, TUNDRA and MOUNTAIN
Greater snow goose Chen caerulescens atlantica
Bêty and Gauthier (2001) assessed the effect of nest visits by researchers on the activity
on nest predators and predation rate of eggs in a colony of greater snow geese in Nunavut
Territory, northern Canada. Although this study involved deliberate nest visits,
inferences can be drawn as to likely behaviour and outcomes if walkers were to pass
through such a dispersed colony. The study was conducted in two breeding seasons, in
years (1996) of moderate, and low (1997) nest predation rates in the region. In 1996 there
was a small increase in Arctic skua Stercorarius parasiticus activity during nest visits
compared to undisturbed areas but this was not apparent in1997. In 1996, activity rate of
another potential avian predator, glaucous gull Larus hyperboreus, was no different
between disturbed and undisturbed conditions, but in 1997 activity and time spent in the
colony was 11.9 times higher during nest visits compared to undisturbed conditions.
There was no significant effect of investigator presence on the activity of common ravens
Corvus corax.
Around 10% of predator observations in the colony involved in attacks on goose nests but
the impact of researcher disturbance was different in each year. In 1996 the probability of
attack tended to be lower during visits but the difference was not significant, whilst in
1997 the probability that a predator attacked a nest was 4.8 times higher during nest
visits. However, the number of successful attacks (eggs predated) was low in both years.
In 1996 only two of four observed attacks during visits were successful, compared to five
of 17 in undisturbed conditions. In 1997 there were three successful attacks out of 11 and
zero out of five respectively. In addition, there were no significant differences in average
clutch size at the end of incubation or nesting success between nests that were visited
eight times compare with those visited three or less times. This study showed that nest
visitation had very little impact on snow goose productivity but the authors suggest that

71
this may not be the case for many arctic birds that, unlike the large and potentially
aggressive snow goose, might not be able to ward off predators as effectively, especially
in years when availability of small mammals is low, and predation pressure on breeding
birds correspondingly high.
Black grouse Tetrao tetrix
Baines and Richardson (2007) experimentally assessed the potential effects of human
disturbance on back grouse in the North Pennines, northern England. In the UK, black
grouse (threatened status) are potentially at risk from increased human recreational
disturbance due to statutory right of human access recently granted through the CRoW
Act. Between 2002 and 2004, 77 black grouse were caught and radio-tagged. Each was
randomly assigned to one of three disturbance treatments of simulated recreational hiking
by approaching individual birds until they were displaced: no disturbance (low),
fortnightly disturbance (moderate) or twice weekly disturbance (high). Birds disturbed
more regularly flushed at greater distances. There were however no differences in
fecundity (clutch size, hatching success, breeding success) or survival, between
treatments. The experimental disturbances had no discernible impact upon the black
grouse populations in the study areas. It is emphasised that this it not to say that more
frequent disturbance might have an impact.
Potential negative impacts of dogs on breeding females have already been partially
mitigated within the Act, which stipulates that dogs should be restrained on short leads
between 1 March and 31 July.
Red grouse Lagopus lagopus scoticus
Watson (1988) recorded declines in Scottish red grouse populations associated with the
presence of people. These declines were however, not attributed to human disturbance
directly but in response to increased corvid numbers attracted to the area by waste food
left by visitors. The presence of more crows led to greater predation of grouse nests.
Common sandpiper Actitis hypoleuca
Yalden (1992) looked at the influence of recreational disturbance on common sandpipers
breeding around a large upland reservoir in the Peak District National Park, England.
During weekends throughout the 1989 and 1990 breeding seasons, sandpiper and angler
censuses were undertaken around the entire shoreline. More detailed behavioural
observations of a few breeding pairs were also made. Anglers were present throughout
the breeding season, with numbers tending to be higher (40-79) in April-May, decreasing
to around 25 by July. The highest count was equivalent to 7.8 anglers/km of shoreline,
but they were not spread evenly; there were some popular angling beaches where nearest
„neighbour distances‟ were around 25 m. Sandpipers took flight about 29% more in areas
with anglers and other visitors, compared with undisturbed shoreline stretches. These
flights often meant that birds encroached onto adjacent territories resulting in far more
territorial disputes. During 37.5 h of observation, adults with chicks were disturbed 59
times mostly (57%) by anglers or hikers. Other sources of disturbance were sheep and
predators (e.g. corvids, weasel Mustela nivalis). Chicks hid upon disturbance from a
single passing person for an average of 3.1 min, in one extreme case a passage of people

72
caused chicks to hide for 34 min. The normal pattern of behaviour is for chicks to be
fed/brooded every 7-8 min; in some cases this was severely disrupted. When anglers or
picnickers settled in a territory, parent sandpipers frequently tried to lead their chicks
away, again often resulting in confrontation with neighbouring territorial pairs. In 1989
there were 31 territories, of which 21 (68%) hatched and 13 (42%) fledged young. In
1990 there were 26 pairs, 15 (58%) hatching and 13 (50%) fledging young. These overall
densities (2.5-3 pairs/km) and productivity are comparable with the best river-nesting
populations. The consequence of human disturbance for this sandpiper population was
that they avoided using popular angling beaches. Based on approximately 6.5 km of
shoreline and with 40 pairs in quiet sections (i.e. below average disturbance – visitor
score of <6/km/visit), there should have been 24 territories along the 4 km of busy shore,
but there were only 17, thus the breeding population size was constrained. However,
breeding success (number of young fledged) of pairs was unaffected regardless of
whether they nested in busy or quiet sections.
Eurasian golden plover Pluvialis apricaria
Finney et al. (2005) used data collected over 13 years to investigate the impact of
recreational disturbance on the distribution and reproductive success of golden plovers
close to a major long-distance footpath, the Pennine Way, in the uplands of northern
England. Whether the response of golden plovers to recreational disturbance was
influenced by changes in the intensity and extent of human activity could be examined as in
1994, to prevent further erosion of surrounding vegetation and soil, a section of the path
(crossing the Snake Summit) was resurfaced. Prior to this resurfacing 32% of all people
(including with dogs) strayed from the path to avoid severely eroded sections and
movement across the moorland was widespread and unpredictable. During the chick-
rearing period, the birds tended to avoid areas within 200 m of the footpath. At this time
there were around 60 visitors/day at weekends and 20/day on weekdays. After resurfacing,
most (96%) hikers remained on the path with a resultant significant decline in disturbance
to the adjacent moorland. In response, golden plovers came much closer to the path,
avoiding a band of about 50 m in width either side of it. The median distance from the path
during five years (for which data was available prior to resurfacing) was 277 m, compared
to 191 m for the five years after. The population size of golden plovers breeding within the
Snake Summit study area doubled during the study period from an estimated 15 pairs in the
late 1980s to 30 in the mid 1990s (Yalden & Pearce-Higgins 1997, Finney et al. 2005).
Golden plover brood survival differed significantly between two study periods. In 1986-
1988 prior to resurfacing 68% fledged, but in 1996-1998 after resurfacing only 46%
fledged. However, there was no evidence of a relationship between brood survival and
distance of the territory from the path. This study suggests that at the intensities of people
recorded, there would be a zone of about 400 m width along an unsurfaced moorland path
where golden plover occupancy would be reduced. Management measure, such as
resurfacing, would help to reduce straying and creation of a network of smaller paths
potentially being created, which might otherwise further exclude birds from suitable
habitat.
Finney et al. (2004) undertook a similar study, again along the Pennine Way, on
Saddleworth Moors using data collected in 1986-1988. This site was similar in terms of

73
habitat but visitor levels were one quarter of that (15 people/day at weekends) (Yalden &
Yalden 1988) recorded at Snake Summit (60/day at weekends) and thus allowed a
comparison of the effect of different disturbance levels on breeding golden plovers. As at
Snake Summit, habitat and topography had an influence on golden plover distribution, but
conversely there was no evidence that they avoided areas close to the path. The evidence
therefore suggests that at this lower disturbance level, there was no significant effect on
golden plover distribution during the chick-rearing period.
Overall, these observations indicate that in more popular areas, such as at Snake Summit,
recreational activity could impact on golden plovers (and potentially other upland
waders) by reducing the availability of suitable breeding habitat. It is thought likely
(Finney et. al 2005) that the 54% drop in occupancy within 200 m either side of the
Pennine Way (equivalent to 29% of the study site area), was sufficient to reduce golden
plover breeding density. Subsequently, Pearce-Higgins et al. (2007) examined to what
extent habitat avoidance is dependent upon visitor numbers at Saddleworth Moors, and
found no evidence that golden plovers avoid disturbed areas where visitor pressure was
half that previously studied. They also investigated whether the large numbers of visitors
(120 per weekend day) using the surfaced footpath impacted on breeding success, despite
the lack of habitat avoidance. There was no evidence that nest location, clutch survival or
chick growth rates were reduced close to the footpath. These results suggest that high
levels of disturbance can impact upon habitat usage, but only in limited circumstances
where visitor pressure is very high (> at least 30 visitors/weekend day). The authors
suggest that access to such areas can be permitted for large numbers of visitors without
impacting upon wader reproductive performance through the provision of a well-surfaced
path.
Yalden and Yalden (1989) used alarm-calling behaviour to estimate the sensitivity of
adult golden plovers to walkers. The average distance at which they began alarm-calling
in response to an approaching person was approximately 200 m during the chick-rearing
period. This is the same distance at which the drop in golden plover occupancy was
recorded by Finney et al. (2005). Finney et al. further suggest that for breeding waders,
similar studies might indicate distances from disturbance sources over which habitat
occupancy is likely to be reduced. For example, response distances include 50 m for
dunlin (Yalden & Yalden 1989), 75 m for common sandpipers Actitis hypoleucos (Yalden
1992), 100 m for New Zealand dotterels (Lord et al. 2001), and over a 1 km for Eurasian
curlew Numenius arquata and common redshank Tringa totanus (Yalden & Yalden
1989). If such alarm-calling behaviour is reflective of sensitivity and settlement during
the breeding season, these distances suggest that the impact of recreational disturbance on
breeding waders will vary depending on the species concerned.
Dunlin Calidris alpina
Finney et al. (2004) as well as studying the effects of disturbance on golden plover, also
studied dunlin in the Snake Summit area of the Pennine Way using the same methods,
during 1987-1988 and 1996-1998. Dunlin distribution was also monitored (1987-1998)
over the spring bank holiday period at the end of May (traditionally a period of high
human visitation, dependent on weather conditions). Use by dunlin of moorland within
200 m of the path increased by around 50% following resurfacing. The median distance

74
of dunlin from the path prior to resurfacing was 175 m, this reduced to 97 m following
resurfacing. As there was no significant change in vegetation composition, this change in
distribution was considered to be due to a reduction in disturbance, as following
resurfacing most hikers kept to the path.
Pearce-Higgins et al. (2007) on Snake Summit, found that dunlin Calidris alpina habitat
utilization in disturbed areas showed a non-significant increase of approximately 50%
following the provision of a surfaced footpath, in a manner similar to that observed for
golden plover.
Eurasian dotterel Eudromias morinellus
Watson (1988) looked at spring densities and breeding success of dotterel in relation to
numbers of people and dogs on Cairn Gorm, Scotland. Over the 10-year study period
(1971-80) human recreational activities increased. Dotterel densities were not correlated to
density of people (which varied from 0.1-6.8/km²/count) or their dogs. Dotterel on their
breeding grounds are very confiding and will allow a very close human approach to the
nest before moving off, this behaviour thus perhaps accounting for this. However, in one
area close to access roads and a chairlift that attracted many people, consequently suffering
extensive vegetation damage and soil erosion, there was some evidence that dotterel
avoided the disturbed ground. Watson observed crows C.corone occasionally predating
nests. Crows were rare in this arctic-alpine zone prior to development of ski-lift facilities in
the 1950s, but subsequently increased greatly in numbers attracted by food left by people.
However, the evidence indicates that over the duration of the study, human impact had not
reduced dotterel numbers or breeding success.
Whitfield et al. (in review) undertook a long-term study of breeding dotterel, also on the
Cairngorm plateau. As many nests as possible were located, date of first laying, clutch
size, hatching success, causes of failure and surrounding vegetation type were recorded.
Distance to nearest footpath and off-path visitor use was used as surrogates for nest
disturbance probability. Around 70% of people stayed close to footpaths, thus disturbance
probability was considered higher closer to paths.
In total 211 clutches were found. Their location was unaffected by path proximity, later
clutches were not further from paths and those nests close to paths were not of
inexperienced pairs. Hatching and fledging success, and daily nest survival were unaffected
by path proximity or density of people (albeit low) off paths. There was a trend towards
poorer hatching success in areas with more people straying off paths but this was not
significant. The causes of nest failure were determined for 76 clutches that failed to hatch.
One clutch was thought to have been destroyed by a dog and two trampled by hikers but
predation by natural predators, followed by desertion due to snowfall, were the main causes
of failure. It is suggested that the high predation and desertion rates (accounting for over a
third of losses of nests found) may have been due to walkers flushing birds from nests
which attracted predators (e.g. common raven Corvus corax) to the nest or lead to
desertion. However, due to their very confiding nature (often allowing a very close
approach by a person to the nest before moving off) and that predation was not related to
path distance or study area, strongly suggests that human disturbance through access on
foot was not a main factor, if at all, in influencing predation rates or desertions. The study

75
further found that there was no correlation between post-fledging survival and nest distance
from a path, and young returning and nesting the next year (identified by colour rings) were
not significantly further from paths. Annual variation in dotterel density and breeding
success were not correlated with numbers of people or their dogs. At levels of human
disturbance observed during this study (concurring with Watson, 1988) dotterel breeding
success in the Cairngorms appears little affected by human disturbance in this region.