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In recent decades, the West European population of Black-tailed Godwits, Limosa limosa limosa, has declined in size at a quite alarming rate, while the Icelandic population, L. l. islandica, has undergone a rapid increase in population size. These two populations have been the subject of a great deal of research, much of which has been focused on understanding the causes and consequences of the contrasting population trends. In 2007, a workshop was held during the annual conference of the International Wader Study Group at La Rochelle, France, with the aims of identifying the likely causes of the population changes and providing recommendations for future actions to improve the conservation of both populations. The available evidence strongly suggests that changes in productivity as a consequence of agricultural intensification are the most likely driver of the decline in L. l. limosa, although the concentration of much of the population in just a few sites in winter and spring is likely to exacerbate their vulnerability to future habitat changes. Agricultural and climatic changes are implicated in the expansion of L. l. islandica, and the availability of both intertidal mudflats and wet grasslands as foraging habitats appears to be very important across much of the winter range of this population. A series of recommendations for actions to conserve both populations are provided, including improving agricultural land management and protecting key passage and winter sites and habitats.
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Bulletin 114 December 2007
Gill et al.: Contrasting population trends of Black-tailed Godwit subspecies limosa and islandica
The last three decades have seen widespread declines in
the population size of many species of shorebird (Interna-
tional Wader Study Group 2003). While research has strongly
implicated the loss and degradation of breeding habitats in
these declines, largely through drainage of wetlands and
conversion to intensive agriculture (Thorup 2006), efforts to
reverse declining population trends have met with little suc-
cess. The West European population of Black-tailed Godwits,
Contrasting trends in two Black-tailed Godwit populations:
a review of causes and recommendations
1 School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
2 Royal Society for the Protection of Birds, The Lodge, Sandy, Beds, SG19 2DL, UK
3 British Trust for Ornithology, The Nunnery, Thetford, IP24 2PU, UK
4 Laboratoire Littoral Environnement et Sociétés, Pôle Sciences et Technologies,
University of La Rochelle, 17042 La Rochelle, France
5 Sociedade Portuguesa para o Estudo das Aves, Av. Liberdade 105, 2º Esq., 1250-140 Lisboa, Portugal
6 Bretagne Vivante – SEPNB, Réserve Naturelle Des Marais De Séné. Brouel Kerbihan- 56860 Séné, France
7 Animal Ecology Group, Centre for Ecological and Evolutionary Studies,
University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands
8 Snæfellsnes Research Centre, University of Iceland, Hafnargata 3, IS-340 Stykkishólmur, Iceland
9 Alterra, Centre for Ecosystem Studies, PO Box 47, 6700 AA, Wageningen, The Netherlands
10 Grupo de Investigación en Biología de la Conservación, Área de Zoología,
Universidad de Extremadura, Avenida de Elvas s/n, 06071 Badajoz, Spain
11 Ligue pour la Protection des Oiseaux, Corderie Royale, BP90263, 17300 Rochefort, France
12 Farlington Ringing Group, Solent Court Cottage, Chilling Lane,
Warsash, Southampton, Hampshire, SO31 9HF, UK
13 Dutch Centre for Avian Migration and Demography, PO Box 40, 6666ZG Heteren, The Netherlands
14 Altenburg & Wymenga Ecological Consultants, PO Box 32, 9269 ZR Veenwouden, The Netherlands
Gill, J.A., Langston, R.H.W., Alves, J.A., Atkinson, P.W., Bocher, P., Cidraes Vieira, N., Crockford, N.J.,
Gélinaud, G., Groen, N., Gunnarsson, T.G., Hayhow, B., Hooijmeijer, J., Kentie, R., Kleijn, D., Lourenço,
P.M., Masero, J.A., Meunier, F., Potts, P.M., Roodbergen, M., Schekkerman, H., Schröder, J., Wymenga, E.
& Piersma, T. 2007. Contrasting trends in two Black-tailed Godwit populations: a review of causes and
recommendations. Wader Study Group Bull. 114: 43–50.
Keywords: Black-tailed Godwit, Limosa limosa, subspecies limosa, subspecies islandica, population size,
population trend, habitat, conservation
In recent decades, the West European population of Black-tailed Godwits, Limosa limosa limosa, has declined
in size at a quite alarming rate, while the Icelandic population, L. l. islandica, has undergone a rapid increase in
population size. These two populations have been the subject of a great deal of research, much of which has been
focused on understanding the causes and consequences of the contrasting population trends. In 2007, a workshop
was held during the annual conference of the International Wader Study Group at La Rochelle, France, with
the aims of identifying the likely causes of the population changes and providing recommendations for future
actions to improve the conservation of both populations. The available evidence strongly suggests that changes in
productivityasaconsequenceofagriculturalintensicationarethemostlikelydriverofthedeclineinL. l. limosa,
although the concentration of much of the population in just a few sites in winter and spring is likely to exacerbate
their vulnerability to future habitat changes. Agricultural and climatic changes are implicated in the expansion of
L. l. islandica,andtheavailabilityofbothintertidalmudatsandwetgrasslandsasforaginghabitatsappearsto
be very important across much of the winter range of this population. A series of recommendations for actions to
conserve both populations are provided, including improving agricultural land management and protecting key
passage and winter sites and habitats.
Bulletin 114 December 2007
44 Wader Study Group Bulletin
Limosa limosa limosa, provides one of the clearest examples
of this problem. The great majority of this population breed
the 20th century (Bijlsma et al. 2001), it was a widespread
and common meadow bird in the 1960s, numbering up to
250,000 individuals (Mulder 1972, Piersma 1986). How-
ever, since then this population has declined severely, and
now numbers only around 50,000 breeding pairs (BirdLife
International 2004).
Attempts to reverse this population decline (and similar
declines in many other meadow-breeding bird species) have
focused on implementing agri-environment schemes (AES)
on farmland in breeding areas to improve breeding success
(Beintema et al. 1997, Kleijn et al. 2001, van Brederode &
Laporte 2006, Verhulst et al. 2007). Despite the area covered
by AES aimed at conserving meadow birds increasing from
c.20,000 ha to c.150,000 ha of farmland in the Netherlands
by 2006, and schemes costing in excess of 30 million Euro
per year, no discernible improvement in the population so far
has been apparent (Kleijn et al. 2001). In fact, the national
population trends of meadow birds in the period 2000–2004
have declined even more rapidly (by approximately 3.5%)
than trends in the period 1990–2000 (Teunissen & Soldaat
2006). In addition to agri-environment initiatives, the cre-
ation and management of nature reserves for meadow birds
has also occurred but on relatively small areas (c.18,000 ha,
Schekkerman et al. subm. b). Although population declines
are less steep in reserves than in the wider countryside, there
is much variability between reserves (Teunissen & Soldaat
By contrast, the population of Black-tailed Godwits that
breeds in Iceland, Limosa limosa islandica, has undergone a
rapid increase over the same time period, from an estimated
2,000–3,000 individuals around 1900 to c.50,000–75,000 at
present. This population has expanded from breeding loca-
tions in south-west Iceland and now occurs virtually through-
out lowland Iceland (Gunnarsson et al. 2005a).
Both the limosa and islandica subspecies of Black-tailed
Godwits have been the subject of extensive research studies in
recent years, mostly focused on the causes and consequences
of population changes (e.g. Beintema 2007, Both et al. 2006,
Gill et al. 2001a, Groen & Hemerik 2002, Gunnarsson et al.
2005b, Roodbergen et al. subm., Schekkerman et al. 2005,
subm. a,b, Schekkerman & Verhulst et al. 2007). In order to
bring together the available information on both populations,
a workshop was held at the International Wader Study Group
conference at La Rochelle, France in 2007. This workshop
aimed to:
ncompare current knowledge of the Icelandic and West
European L. limosa populations
ninform potential explanations for the divergent popula-
tion trajectories
n highlight research gaps and potential future collabora-
nrecommend conservation measures.
larly focusing on identifying the likely drivers of changes in
demography and distribution of both populations, highlight-
a series of recommendations for future conservation and
research efforts. The workshop attracted c.100 participants
with a wide range of expertise and knowledge of these birds
and their habitats. This meeting was therefore a unique and
exciting opportunity to compare two subspecies with widely
diverging population trajectories, and to discuss causes of
changes and prioritise future actions.
The workshop comprised a series of comparative talks
which detailed current knowledge of the key processes
and demography, and patterns of connectivity between sea-
sons and sites, for the two populations. During the workshop,
information from each talk was used to complete a summary
table of current status, drivers of change and potential impact
for a series of demographic, distribution and habitat issues
(Tables 1 & 2). The key issues arising from this summary are
discussed below.
The West European breeding population of Black-tailed
Godwits breeds throughout the Netherlands, with smaller
numbers in Germany, Belgium, Denmark, France and the
UK, and migrates via France and Iberia to winter grounds
in Senegal, Guinea-Bissau and Guinea in sub-Saharan West
Africa (Beintema & Drost 1986, Kuijper et al. 2006).
Key breeding season issues
This population depends on grasslands with high ground-
water levels as breeding sites, and on wetlands as passage
and winter foraging sites (Wymenga et al. 2006). Over the
last 50 years, both of these habitats have undergone extensive
population is on clay-on-peat and peat soils, but the historical
distribution also included blanket bogs and wet moorland,
which were abandoned as the population expanded into agri-
al. 2001). Since then, drainage, urbanisation and conversion
of grasslands to arable crops have created drier and highly
fragmented breeding habitats (SOVON 2002). The remaining
grasslands are generally farmed very intensively, with mow-
ing dates having advanced by one month over the last century,
most grasslands now being mown more than twice per year,
and livestock number per unit grassland area being the highest
of all European countries (Statistics Netherlands, Statline).
In addition, there is evidence that changes in predator control
and environmental contamination, and landscape changes
such as road-building and tree-planting, have altered preda-
tor abundance and distribution, and consequently increased
nest and chick predation rates (Schekkerman et al. subm. a,
Teunissen et al. 2006, Teunissen & Willems 2004).
When the population size was higher, godwits bred on
grasslands in areas of peat, clay and sandy soils. The popu-
lation decline has been characterised by a contraction into
largely peat areas, although levels of degradation now appear
similar across all soil types. AES initiatives to reverse the
population decline have focused on delaying mowing dates
and improving nest protection. However, there is no strong
evidence that these schemes have improved breeding densi-
ties (Kleijn et al. 2001, Kleijn & van Zuijlen 2004, Verhulst
et al. 2007, Willems et al. 2004), despite evidence that
delayed mowing saves nests and improves chick survival
(Schekkerman & Müskens 2000, Schekkerman et al. 2005,
subm b). Godwits preferentially choose areas with high
groundwater levels as breeding sites (Kleijn & van Zuijlen
Bulletin 114 December 2007
Gill et al.: Contrasting population trends of Black-tailed Godwit subspecies limosa and islandica
2004, Verhulst et al. 2007); although clay soils with relatively
low ground water levels can also be used. Current AES do not,
however, include management of groundwater levels, as this
is a contentious issue for farmers. Successful management
diverse swards within the matrix of more intensively farmed
hatched throughout an area with access to high quality forag-
ing sites as well as shelter from predators (Schekkerman et
al. subm. b).
Key non-breeding season issues
On passage and at wintering sites in Iberia and West Africa,
wetlands have been extensively drained and dammed since
the 1960s, to facilitate energy production, water storage and
agriculture (Kuijper et al. 2006). Rice production is now
which,whenooded,iswetenough toallowbirdssuchas
godwits to forage. Godwits have been reported foraging on
al. 1985, Tréca 1984, van der Kamp et al. 2007), and recent
studies of godwits in Iberia and Africa have shown that
the birds primarily consume rice seeds (along with smaller
amounts of invertebrate food) during the months in which
on molluscs, worms and other invertebrates, and the conse-
quences of this largely plant-based diet through much of the
winter and spring are currently unknown.
Godwits begin to arrive in West Africa in July, and they use
and harvest (Nov–Dec) (Kuijper et al. 2006, van der Kamp
et al.2007).WhentheAfricanriceeldsaredriedoutand
harvested during December, the birds begin to migrate north
et al. 2007, Zwarts et al. in press). At this time they can be
National and Natural Park, SW Spain, in December, up to
25,000 in Extremadura, W Spain, by early February and up
to 45,000 around the Tagus and Sado estuaries, W Portugal,
by late February. Passage sites in Morocco were formerly
used in autumn and spring but few birds use these sites
this shift in passage site use, as may recent increases in rice
production in Spain. Similarly, use of French sites on spring
migration may have declined in recent years, although overlap
Table 1. Summary of the current status of the demography, distribution and habitat use of the West European Black-tailed Godwit
population, Limosa limosa limosa, together with likely drivers of changes and estimates of the proportion of the population experiencing these
Status of limosa population Drivers of changes Potential population
Population size c.60,000 breeding pairs
Population trend Severe decline at c.5%p.a. Primarily due to declining productivity Population-wide
Nest survival Intermediate to low and variable. Earlier mowing and increased predation Population-wide
Chick survival Low. Declines since 1980s Earlier mowing, reduced habitat heterogeneity and
increased predation
Productivity trend Decline since 1980s from c.0.7 to 0.2
of remaining grasslands
Juvenile survival Estimates from 40% to 68% Huntingofjuvenilesonmigrationcouldbesignicant Higher estimate from one
site only (Workumerwaard)
Adult survival Annual estimates = 81–96% Unknown Probably population-wide
Breeding habitat Grasslands with high ground water levels
in open landscapes
26% loss to urbanisation and arable conversion since
1960s. Severe decline in quality through drainage and
Breeding locations Grassland in Netherlands, Germany,
Belgium and Denmark
Unknown as degradation of all soil types appears similar Population wide
Breeding trend Declining and contracting in range Declining habitat quality, fragmentation Population-wide
Autumn habitat Wetlands,mudats,saltpans,riceelds Unknown Unknown
Autumn locations France (Jun–Nov), Iberia (Jun–Nov) and
W Africa (Jul–Nov)
changes in site quality
Africa. Juveniles may use
European sites
Autumn trend Earlier departure and reduced use of
Early departure correlated with poor breeding success
and deferral of breeding
Winter habitat Riceeldsandwetlands Increased use of rice following widespread conversion
of wetlands
Winter locations Senegal and Guinea Bissau (Nov–Dec),
Iberia (Dec–Feb)
Large-scale damming, drainage, water storage and
agriculture in Senegal delta
Winter trend Possible earlier departure from Africa for
changing rainfall patterns may be involved
Spring habitat Riceelds,saltpansandwetlands Conversionofwetlandstoriceelds Population-wide
Spring locations Iberia (Dec–Feb), France (Feb–Mar) and
Netherlands (Mar–Apr), reduced use of
Morocco and France
changes in site quality
Switch to rice-seed diet
Spring trend Possible earlier departure from Iberia but
arrival in Netherlands unchanged
Unknown Unknown
Bulletin 114 December 2007
46 Wader Study Group Bulletin
between the two subspecies at this time of year makes this
These extensive habitat changes throughout the range of
L. l. limosa allow several plausible causes of the severe
n declining habitat quality and availability in the breeding
season may have resulted in reductions in productivity;
nchanges in winter and spring diet may have altered the
body condition or survival probability of fully-grown
nhabitat and climatic changes in the Sahel region may have
altered habitat availability, and consequently body condi-
tion or survival of fully-grown birds.
The demographic evidence presented at this workshop strong-
ly suggests that reductions in productivity are the most likely
driver of the population decline. Changes in productivity
through the period of breeding habitat change have been
severe, declining from c.0.7 chicks per pair (range: 0.5–1) in
the 1980s to c.0.2 chicks per pair (range: 0.1–0.7) at present
(Schekkerman et al. 2005, subm b). Changes in the timing
and frequency of mowing, affecting both direct nest and chick
losses and the foraging conditions for chicks (Schekkerman
& Beintema 2007), are strongly implicated in driving these
declines. In addition, the abundance of nest and chick preda-
tors and their impact on an increasingly fragmented and
exposed (through loss of cover by early mowing) population
appears to be growing. In recent years, there has also been
evidence from one site for deferral of breeding by up to half
of the adults returning to the breeding grounds.
The widespread use of rice as food in winter and spring may
affect adult body condition but there is currently no evidence
for any declines in adult survival rates, in fact adult survival
appears to have increased in recent decades (Zwarts et al. in
press). Recent colour-ring studies suggest high adult annual
survival rates of c.81–96% (Both et al. 2006, Roodbergen et
al. subm., J. Schröder in prep.), though national estimates
from ring-recoveries suggest annual survival rates of c.80%
(van Noordwijk & Thomson subm.). Recent reductions in
the length of the hunting season in France are likely to have
reduced hunting pressure, and numbers of hunting recoveries
of ringed birds have declined in recent years (Zwarts et al.
in press). Mortality of juveniles on autumn migration may
Table 2. Summary of the current status of the demography, distribution and habitat use of the Icelandic Black-tailed Godwit population, Limosa
limosa islandica, together with likely drivers of changes and estimates of the proportion of the population experiencing these conditions.
Status of islandica population Drivers of changes Potential population impact
Population size c.50,000–75,000 individuals
Population trend Rapid increase, from c.2600 around 1900 Warmer temperatures and agricultural
expansion in Iceland
Nest survival 50–75% of nests hatch Unknown Unknown
Chick survival 20–80%pairsedgeatleastonechick.
Productivity likely to be c.0.5–0.8chicks/pair
Population expansion may have reduced
average productivity
Productivity trend Unknown Unknown Population-wide
Juvenile survival c.60%fromringingtoedgingandc.50%
Unknown Population-wide
Adult survival Annual estimates = 87–99%, highest in winter
and lowest during spring migration
Survival increased in late 1990s.
Some evidence of recent declines
Probable regional variation in
survival trends
Breeding habitat Lowland marshes and dwarf-birch bogs Suitability of dwarf-birch bogs as breeding
sites may have increased
Breeding locations Expansion from SW to NE Iceland Expansion into colder parts of Iceland with
more dwarf-birch bog
Breeding trend Increasing and expanding distribution Average productivity likely declined but
number of pairs increased
Autumn habitat Estuarinemudats,occasionaluseofriver
valleys and gravel pits
None Most use of freshwater habitats by
Autumn locations Most in UK, Ireland and France (Jul–Sep). None Population-wide
Autumn trend Expansion into E and NW England moulting
Population size increase c.30% of population in new sites
Winter habitat Estuarinemudatsandgrasslands.
Saltpans in Iberia
Grassland use more extensive in recently
occupied sites
c.80%onmudatsandc.20% on
Winter locations UK, Ireland, France and Iberia (Oct–Feb) Population size increase Population-wide
Winter trend Recent expansion into E and NW England Population size increase c.10% of population in new sites
Spring habitat Estuarinemudatsandgrasslands.Someuse
Grassland use more extensive in recently
occupied sites
c.30%onmudatsandc.70% on
Spring locations Netherlands (Iberian and French birds),
Ireland (Irish birds), UK (UK and Irish birds)
Increase in use of Netherlands and E England
c.50–60% of the population uses
Netherlands and E England sites
Spring trend Increasing use of grasslands on spring passage.
Earlier arrival in Iceland
warmer springs
Earlier arrival trend may be more
apparent in the earliest birds
Bulletin 114 December 2007
Gill et al.: Contrasting population trends of Black-tailed Godwit subspecies limosa and islandica
be higher as they appear to use European passage sites more
than adults, and may thus be exposed to hunting pressures in
France. The available national ringing recovery data, together
with a recent colour-ringing study from one site, suggest that
juvenile survival is not particularly low, but these estimates
may not be representative of the whole population.
Habitat structure and composition in Iberia and West Africa
have clearly changed dramatically since the 1950–1960s,
especially in the Senegal delta, but again there is little evi-
dence for negative impacts on survival rates, at least in recent
years. Mortality rates do appear to be a little higher in years
with low rainfall in the Sahel, possibly as a consequence of
birds occurring at high densities in the remaining wet areas,
especially during the post-breeding arrival period when con-
hunting pressure (Zwarts et al. in press). However, although
there is no strong evidence for climatic or habitat changes
in the non-breeding season driving the population declines,
there is clear concern that these processes could exacerbate
the declines, as such a high proportion of the population is
times of year.
The Icelandic population of Black-tailed Godwits breeds pri-
marily in Iceland, with small numbers in the Faeroes, Lofoten
and Shetland Islands. In Iceland they breed in lowland areas,
primarily on coastal marshes and dwarf-birch bogs (Gunnars-
son et al. 2006a).
Key breeding season issues
In both marshes and dwarf-birch bogs, Icelandic Black-tailed
Godwits are strongly associated with shallow pools, often
surrounded by sedges, which support foraging adults. Chicks
feed mostly on invertebrates gleaned from vegetation, and
seek out tracts of grassland which are rarer in the dwarf-birch
bog habitats. The expansion from SW Iceland (around 1900)
to the major basins in the north and west (1920s–1940s) and
then the east and north-east of Iceland (1970s–1980s) was
characterised by an increase in the proportion of dwarf-birch
bog sites occupied (Gunnarsson et al. 2005a). The most
recently occupied sites are also colder than the traditionally
occupied southerly sites (Gunnarsson et al. 2006b). The
lowland areas of Iceland have seen widespread drainage of
1960s, and godwits are now frequently recorded feeding on
Key non-breeding season issues
After the breeding season, Icelandic godwits migrate south
to the UK, Ireland and France. Small numbers of birds also
appear to migrate directly to Portugal from Iceland. The
moulting sites in the north-west and east of England have
seen particularly large increases in use in recent decades,
especially the Wash, Humber and Dee estuaries. The vast
the autumn months. By winter many birds have moved
south to estuaries in France and Portugal and, in Ireland and
England, they start to forage on grasslands. The number of
Icelandic godwits wintering in the UK, Ireland and France is
to assess because the subspecies overlap there, particularly
during January and February when both wintering and migra-
tory continental godwits are present.
In spring, most godwits from Portugal and France migrate
to the Netherlands or eastern England, where they forage
primarily on grasslands. At the same time, many birds from
grasslands suggest that godwits move to grasslands when
estuarinefood suppliesarenolongersufcienttosupport
lands throughout winter and spring. This seems to be par-
ticularly common in the northern part of their range, where
estuarine prey are often subject to strong seasonal depletion
(e.g. Gill et al. 2001b) and where grassland foraging appears
to be a necessary addition to compensate for insufficient
estuarine food supplies.
The drivers of the population increase in Icelandic god-
nclimatic amelioration in Iceland may have improved
breeding conditions and increased the area available for
breeding godwits;
nchanges in habitat structure in Iceland may have improved
breeding conditions;
nclimatic and habitat changes in the non-breeding range
may have improved survival and condition for breed-
nchanges in hunting pressures may have improved survival
The initial increase in godwit numbers around the 1920s co-
incided with a period of rapid warming in Iceland, suggesting
that climatic amelioration may have been involved, at least in
the early stages of population growth. From the 1930s to the
1980s, the rate of colonisation of Iceland is correlated with
the number of drainage ditches installed, indicating that large-
breeding distribution. The common observation of godwits
bogs, suggests that the presence of hayfields as foraging
habitats may have improved the quality of dwarf-birch bogs
as breeding sites.
In recent decades, the primary habitat change in lowland
Iceland has been the development of afforestation schemes,
many of which are focused on marsh habitats, in addition to
house-building in lowland areas. Since the 1980s, there has
been a strong positive correlation between Iceland spring
temperatures and the index of Icelandic godwits wintering
in the UK (as recorded by the Wetland Bird Survey, Banks
et al. 2006). Colour-ring information has shown that the
majority of the UK population increase has involved birds
from the recently occupied east and north-east of Iceland
(Gunnarsson et al. 2005b); strongly suggesting that recent
climatic amelioration has allowed these coldest parts of the
country to be occupied.
In the non-breeding range, there are few indications of
improvements to habitat quality, but changing rainfall pat-
Bulletin 114 December 2007
48 Wader Study Group Bulletin
terns may be altering the timing of availability of grassland
foraging sites. This may be particularly true of sites in eastern
England and the Netherlands, use of which has increased
substantially in recent years (Gerritsen & Tijsen 2003, Gill
et al. 2001). The reduced frequency of cold winters in NW
The role of hunting pressure in driving population changes
are records of godwits being considered a delicacy, having
been described as “highly esteemed for the table” and “both
shot and taken by snares” (Morris 1897). It is possible that
reductions in hunting pressure, and the associated disturbance
levels, may have influenced the population changes, but
there are currently no data with which to explore this issue.
At present, the only country in which Icelandic godwits are
shot is France, and the lack of accurate bag statistics precludes
calculation of the impact of this hunting pressure. Although
the Icelandic population is increasing, it is still small and
restricted in range, and the impact of hunting is therefore
Despite the current contrast in the fortunes of these two popu-
lations, comparison of their demography and distribution has
revealed intriguing similarities, which we hope will help to
focus current and future conservation and research efforts. In
both Iceland and the Netherlands, it seems evident that agri-
expansions and contractions over the last century. Wetlands
and heathlands have been converted into agricultural habitats
in which productivity has increased through fertilisation and
mowing maintains an open sward structure. This seems to
cies, probably through higher abundances of soil macrofauna
and improved access to these resources (Beintema 1986,
Beintema et al. 1987). Throughout Europe this process began
greater in the more populated countries of NW Europe than in
Iceland. In both Iceland and the Netherlands, there is evidence
that populations of Black-tailed Godwit, along with other
similar species, may have been able initially to increase and
expand their distribution in response to this habitat conversion
and increase in productivity.
In the Netherlands, the agricultural landscape is now so in-
tensively managed that the area suitable for breeding godwits
has declined dramatically, such that the population is now
probably lower than it was prior to the 1950s. By contrast,
changes in agricultural practice that have created a landscape
in which grass production and moderate levels of horse graz-
ing have given rise to the complex sward structure necessary
for breeding, alongside areas suitable for foraging. The extent
to which these habitat changes have driven the population
increase in Iceland is not currently clear, and there may yet
be scope for further population expansion in Iceland. How-
ever, the Netherlands experience would strongly suggest that
are likely to be very detrimental to godwits and other ground-
nesting birds. In addition, land-use changes in Iceland, such as
the current widespread afforestation programmes, are a major
threat to the internationally important shorebird populations
of lowland habitats.
While habitat changes may be the primary driver of popu-
lation changes over the last century, climatic changes have the
potential to be an equally important issue in the near future.
Temperature increases and changing precipitation patterns are
both implicated in the islandica population increase, and there
is some recent evidence for deferral of breeding in limosa
in particularly dry years, although warm conditions are also
likely to improve chick growth and survival. The timing of
spring rainfall and the magnitude of temperature changes in
the future are therefore likely to be very important in deter-
mining the impact of climate change on breeding success. The
dependence of most of the limosa population on relatively
likely to make them highly vulnerable to changing rainfall
patterns. The recent drought in the Sahel region (Dai et al.
2004) is of particular concern for the maintenance of suitable
foraging areas for these birds. Rice production is also depen-
dent upon global markets and, in Iberia, on European Union
agricultural support mechanisms, further increasing concern
over the persistence of these key habitats.
A more immediate threat to the godwits that depend on rice
of a new airport near Lisbon. One potential location for this
airport is in the vicinity of the Tagus Estuary Nature Reserve,
areas in the Tagus and Sado estuaries, which are used by tens
of thousands of godwits during January and February, and
used by godwits throughout the non-breeding season. Such a
development could seriously impact on a very large propor-
tion of the godwit population at a critical time of year, and
would therefore be very likely to exacerbate already severe
population declines.
The historical context of the population changes, and
concern about future conditions for godwits and other similar
bird species, led the workshop participants to identify the
key recommendations that we believe it will be necessary
to implement in order to conserve Black-tailed Godwits
effectively in Iceland and W Europe.
1. Improve prescriptions and targeting of AES in the breed-
ing range, focusing efforts in areas with high groundwater
levels and open landscapes to attract godwits and avoid
high predator densities, in order to have the potential to
improve overall productivity. Include raising groundwater
levels in the Netherlands AES prescriptions (as is the case
in the UK, Denmark and Germany)
2. Incorporate the creation of small-scale habitat mosaics
into management prescriptions, to provide both foraging
and predator avoidance options throughout the season.
3. Improve conservation of key wetland habitats in Iberia
and Africa, either through maintenance of support for rice
production or restoration of wetlands, as well as designa-
tion of more sites under relevant national legislation and
international treaties (EU Birds and Habitats Directives,
Ramsar Convention etc.).
4. In view of the severe continuing declines of this population,
take a precautionary approach and ban hunting of godwits,
at least temporarily, where there is any risk that birds from
Bulletin 114 December 2007
Gill et al.: Contrasting population trends of Black-tailed Godwit subspecies limosa and islandica
this population could be involved (especially late migrat-
ing juveniles in autumn), until productivity is increased
to a level that can sustain a certain amount of additional
mortality of adults and immatures.
1. Improve conservation of winter habitat mosaics, particu-
larly in areas, such as Ireland, England and France, where
grasslands, coastal lagoons and salinas may be necessary
to maintain populations when estuarine food supplies are
2. Reduce impact of afforestation and building developments
in Iceland on godwits and other shorebird species, by
conserving key breeding areas.
3. Improve protection of coastal habitats in areas where
development and associated disturbance levels are high
(especially in Ireland).
1. Improve estimates of juvenile survival, causes of mortality
and distribution prior to recruitment.
2. Improve survey information on the distribution and
abundance of Black-tailed Godwits in the West African
wintering grounds.
3. ImproveunderstandingoftheimportanceoftheDoňana
National and Natural Park area for protecting L. l. limosa
during spring migration.
4. Explore the potential impact of hunting on the limosa
population, and work with hunting organizations to
develop better methods of recording accurate bag statistics
in France.
5. Explore the impact of the increasing time-lag between
godwit arrival in the Netherlands and the commencement
of breeding, and the frequency of deferral of breeding
6. Improve understanding of the location, timing and dura-
tion of use of passage sites in Europe and Africa, and
habitat use and diet within these sites.
1. Improve understanding of the role of agricultural intensi-
2. Identify the key drivers of productivity in different habi-
tats in Iceland.
3. Improve survey data for Iberia and France during the
passage period of January to March, when there is the
greatest overlap between the subspecies.
4. Explorethefactorsinuencingthequalityandavailability
of grassland habitats.
5. Explore the consequences of seasonal matching (indi-
vidual use of similar quality habitat in both breeding and
tion of key areas for conservation.
6. Explore the potential impact of hunting on the islandica
The workshop provided an exciting and hopefully very valu-
able means of exploring the causes of population change in
two closely related subspecies. The large group of experts
provided an ideal forum for both highlighting key issues
and using expert opinion to identify and prioritise the con-
servation recommendations. This process would undoubt-
edly have been helped were information available on the
eastern population of L. l. limosa and the eastern subspecies,
L. l. melanuroides.Ournalrecommendationisthereforeto
encourage the collation and presentation of information on
these two populations.
Many thanks to all the workshop participants who contributed
so willingly and helpfully to the whole day, Bill Sutherland
for historical godwit recipes, Richard Chandler for helpful
comments and to the organising committee of the IWSG
conference for providing such excellent conditions for eating,
drinking, colour-ring reading and discussion.
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... Among them, the Dutch population of continental Black-tailed Godwit Limosa limosa limosa (afterwards called 'godwit') is one of the most well-studied (sub-)species and can serve as a representative of Dutch farmland birds as it historically shares breeding habitats with many other farmland birds (Howison, Belting, et al., 2018;Roodbergen & Teunissen, 2019). The Dutch population of godwits, which comprises 87% of the East-Atlantic Flyway population, has declined by ~70% since the late 1960s (Gill et al., 2007;Kentie et al., 2016), attributed to reproduction that does not compensate the annual losses Loonstra et al., 2019). Low recruitment reflects low nest and chick survival as a result of habitat degradation and intensive farming-associated disturbance during the breeding season (Groen & Hemerik, 2002;Kentie et al., 2013). ...
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1. Agricultural intensification has modified grassland habitats, causing serious declines in farmland biodiversity including breeding birds. Until now, it has been difficult to objectively evaluate the link between agricultural land-use intensity and range requirements of wild populations at the landscape scale. 2. In this study of Black-tailed Godwits Limosa limosa, we examined habitat selection and home range size during the breeding phase in relation to land-use intensity , at the scale of the entire Netherlands. From 2013 to 2019, 57 breeding godwits were tracked with solar-Platform Transmitter Terminals (26-216 locations [mean: 80] per bird per breeding phase) and used to estimate their core (50%) and home ranges (90%). Of these, 37 individuals were instrumented in Iberia and therefore unbiased toward eventual breeding locations. The tracks were used to analyse habitat selection by comparing the mean, median and standard deviation of land-use intensity of core and home ranges with matching iterated random samples of increasing radii, that is, 500 m (local), 5 km (neigh-bourhood), 50 km (region) and the whole of The Netherlands. 3. Land-use intensities of the core and home ranges selected by godwits were similar to those at the local and neighbourhood scales but were significantly lower and less variable than those of the region and the entire country. Thus, at the landscape scale, godwits were selected for low-intensity agricultural land. 4. The core range size of godwits increased with increasing land-use intensity, indicating high agricultural land-use intensity necessitating godwits to use larger areas. 5. This is consistent with the idea that habitat quality declines with increasing land-use intensity. This study is novel as it examines nationwide habitat selection and space use of a farmland bird subspecies tracked independently of breeding locations. Dutch breeding godwits selected areas with lower land-use intensity than what was generally available. The majority of the Dutch agricultural grassland (94%) is managed at high land-use intensity, which heavily restricts the viability of breeding possibilities for ground-nesting birds. The remote sensing methodology 26888319, 2023, 1, Downloaded from
... Smaller and more isolated populations can be found in most European countries, not only in agricultural habitats but also in natural ecosystems such as bogs and fens (Jensen and Perennou 2007;Ławicki and Kruszyk 2011;Strus et al. 2018). Despite the species ability to thrive under a wide range of environmental conditions, it has been declining throughout most of its range in the last half-century (Gill et al. 2007). In the intensive grasslands of the Netherlands, population size decreased by 30% between 2007 and 2015 (from an estimated 47 to 33 thousand breeding pairs; (Kentie et al. 2016)). ...
The endangered continental Black-tailed Godwit (Limosa limosa limosa) is a migratory ground-nesting wader breeding in a wide variety of open, wet habitats across Europe. Conservation research has concentrated on the causes of population decline, but we know surprisingly little about whether any resources limit local breeding populations and if so, whether these are resources for the adults or the chicks. We collected data from 63 key breeding sites in five countries across Europe to test whether, after correcting for differences in surveyed areas, the size of Godwit breeding populations was related to environmental variables (vegetation biomass, soil moisture) or food resources for adult birds (soil invertebrates) or chicks (vegetation dwelling arthropods) measured during different times of the reproductive cycle. We found the number of Godwit territories to be positively related to arthropod abundance during the chick-hatching period. We found additional, weaker support for a positive relation between Godwit territory numbers and the abundance of soil-dwelling invertebrates (mostly earthworms) at clutch laying, but not at chick-hatching. These relationships were observed across countries, while we found little support for relationships within countries, possibly due to the smaller range in conditions that exist within countries. Both vegetation growth and soil moisture weren’t related to Godwit territory numbers. Our results suggest that food abundance for chicks, and to a lesser extent adult birds, are key factors determining the size of local Godwit breeding populations. Conservation management aiming to enhance local Godwit populations should therefore consider the impacts of management strategies on the arthropod prey of chicks.
... This is mostly caused by the deterioration of the estuary environment. Since the distance between bridges constructed downstream may also restrict the wintering of whooper swans, it is necessary to limit the construction of new bridges (Hong, 2020 in biodiversity loss and potential nutrient degradation (Terborgh et al., 2001) as well as loss of ecosystem services related to the quality of life (Dobson et al., 2006;Layman et al., 2007 (Gill et al., 2007), and artificial changes (Both et al., 2006). Since species that are sensitive to environmental changes such as rare and endangered species are vulnerable to habitat isolation (Luther et al., 2020), they tended to prefer wide areas where the ecosystem was relatively intact. ...
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Background and objective: Fragmentation of river ecosystems is expected to affect biodiversity loss, but bridge construction is proceeding without consideration in urban areas. This study was conducted to determine the effect of internal environmental factors and river ecosystem fragmentation caused by bridge construction on the population of wintering whooper swans ( Cygnus cygnus ) in the Nakdong River of Busan Metropolitan City, a key wintering site for whooper swans.Methods: To compare the wintering population according to the distance between bridges, we surveyed and analyzed the current status of the population by period, distance between bridges, and land cover. One-way ANOVA and post-hoc test were conducted to confirm whether the differences in the environmental factors of the wintering sites, such as the distance between bridges, land cover status, and the number of wintering individuals, were statistically significant.Results: 83.6-94.7% of the wintering population in the lower Nakdong River were observed in Sec. 2 (Nakdong River Estuary Bank-Seobusan Nakdong River Bridge, 5.3 km) and Sec.4 (Gamjeon-Iron Bridge-Nakdong River Hwaengdansugwan Bridge, 3.6 km). As for the distance between the feeding and resting places of whooper swans and the bridges, whooper swans used the waterside and wetlands at an average distance of 1,147.5 m (10.9-2,611.2 m) from the bridge.Conclusion: Considering the weight of male swans and the presence of young individuals, as well as disturbance factors such as the noise and speed of vehicles crossing the bridges, it is necessary to maintain at least a 4 km distance between bridges for stable wintering. In addition, since fragmentation of river ecosystems has been confirmed to have an adverse effect on biodiversity, it would be desirable to keep the ecosystem intact and connected.
... While the geographical and ecological characteristics of the breeding grounds of these two Asian godwits subspecies are considerably different (Zhu et al., 2022), their non-breeding distributions overlap to a large extent. This pattern is also seen in islandica and limosa in the East-Atlantic Flyway (Gill et al., 2007). Outside their core breeding grounds in Iceland and the Netherlands, the two subspecies co-occur from the UK to Morocco during the non-breeding season (Lopes et al., 2013;Verhoeven et al., 2021). ...
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Until recently, Limosa limosa melanuroides was thought to be the only subspecies of Black-tailed Godwit in the East Asian–Australasian Flyway. For this reason, all previous occurrences and counts of Black-tailed Godwits in the flyway have been assigned to melanuroides. However, a larger-bodied subspecies, bohaii, has recently been discovered in the flyway. As a result, the occurrence of Black-tailed Godwits in the flyway needs to be reconsid- ered such that the specific distribution of each subspecies becomes known. To this end, we developed a simple discriminant function to assign individuals to subspecies based on their bill and wing length. Cross-validation with individuals known to be bohaii or melanuroides, based on molecular analysis, showed the developed function to be 97.7% accurate. When applied to measurements of godwits captured at 22 sites across 9 countries in East–Southeast Asia and Australia, we found that bohaii and melanuroides occurred at most sites and overlapped in their distribution from Kamchatka to Australia. We examined photos from all along the flyway to verify this surprising result, confirming that both subspecies co-occur in most locations. Based on these results, we hypothe- sise that bohaii and melanuroides from the west of their breeding ranges mostly migrate over mainland China. Birds of both subspecies from the east of their ranges are expected to migrate along the Pacific Ocean. We encour- age ringing groups in East–Southeast Asia and Australia to use this simple method to keep adding knowledge about Black-tailed Godwits in the East Asian–Australasian Flyway.
... Conservation actions should take place particularly in the management of breeding habitats such as have been applied in some Western European countries (Roodbergen et al., 2012). They should lead to the improvement of survival, breeding, and migration of this species (Gill et al., 2007), increase the coverage of agri-environmental schemes (Kleijn et al., 2010) and ensure the conservation and monitoring of migratory staging areas (Estrella and Masero, 2010). ...
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Throughout the last decades, the increasing pressure of anthropogenic (climate and land-use) changes has been a major impact on biodiversity in several regions and habitat types. These drivers have disturbed the timing of reproduction in animals and plants as well as the migration of animals resulting in changes in population size and species distribution. Our study analyses the impact of climate change in the spatial distribution of selected species, between historical period (1950 – 2018) and future period (2041 – 2070), in four case studies at a watershed level over the Atlantic region, highlighting the importance of integrating landscape trends to anticipate key biodiversity pattern responses. The results were compared to predicted future climate projections (2041 – 2070), based on two IPCC scenarios (RCP4.5 and RCP8.5), using a 5-model ensemble developed under the EURO-CORDEX project. Further, complementary downscaling methodologies were applied, allowing the increase of the spatial resolution from ~12 km to ~1 km in all climate variables. Land cover maps were developed using the Forecasting Landscape Scenarios Model. We assessed the impact of projected climate change and land cover development on specific vulnerable species distribution for each case study. The results showed an overall temperature increase for all case studies and both representative concentration pathways scenarios and a shift in potential habitat area of species addressed to areas upstream of the catchments. These predictions have a strong importance in defining conservation strategies of these vulnerable species, and may overall bring guidelines for the management of Atlantic landscapes in response to climate change, namely as pertinent ecological indicators under realistic future changing regional scenarios.
... This expected reduction in suitable breeding habitat contrasts interestingly with observations made for a different subspecies, the Icelandic godwit Limosa limosa islandica. At the start of the 20th century, the breeding area for islandica was constrained to Iceland's relatively warm southwest corner, and the population numbered only a few thousand (Gill et al., 2007). As the climate warmed and many areas were converted to farmland, large parts of the island became more suitable for breeding, and the islandica population consequently grew to ca. 47,000 (Gunnarsson et al., 2005;Gunnarsson et al., 2006). ...
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Habitat loss and shifts associated with climate change threaten global biodiversity, with impacts likely to be most pronounced at high latitudes. With the disappearance of the tundra breeding habitats, migratory shorebirds that breed at these high latitudes are likely to be even more vulnerable to climate change than those in temperate regions. We examined this idea using new distributional information on two subspecies of Black‐tailed Godwits Limosa limosa in Asia: the northerly, bog‐breeding L. l. bohaii and the more southerly, steppe‐breeding L. l. melanuroides. Based on breeding locations of tagged and molecularly assayed birds, we modelled the current breeding distributions of the two subspecies with species distribution models, tested those models for robustness, and then used them to predict climatically suitable breeding ranges in 2070 according to bioclimatic variables and different climate change scenarios. Our models were robust and showed that climate change is expected to push bohaii into the northern rim of the Eurasian continent. Melanuroides is also expected to shift northward, stopping in the Yablonovyy and Stanovoy Ranges, and breeding elevation is expected to increase. Climatically suitable breeding habitat ranges would shrink to 16% and 11% of the currently estimated ranges of bohaii and melanuroides, respectively. Overall, this study provides the first predictions for the future distributions of two little‐known Black‐tailed Godwit subspecies and highlights the importance of factoring in shifts in bird distribution when designing climate‐proof conservation strategies.
... Regional differences in the timing of cultural wet grassland expansion and decline have thus led to frontiers of emergence and degradation of wet grassland landscapes, and very few wader populations have remained viable or shown increases (Gunnarsson et al., 2005;Johannesdottir et al., 2019). The sequence of rise and fall of grasslands is paralleled by the pattern that some European regions exhibit declines in breeding migratory waders (Gill et al., 2007;Schekkerman et al., 2009). Waders have an umbrella species function: management for threatened waders has a strong supporting impact on meadow plants and amphibians (Rannap et al., 2017). ...
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This study aims at supporting the maintenance of representative functional habitat networks as green infrastructure for biodiversity conservation through transdisciplinary macroecological analyses of wet grassland landscapes and their stewardship systems. We chose ten north European wet grassland case study landscapes from Iceland and the Netherlands in the west to Lithuania and Belarus in the east. We combine expert experiences for 20–30 years, comparative studies made 2011–2017, and longitudinal analyses spanning >70 years. Wader, or shorebird, (Charadrii) assemblages were chosen as a focal species group. We used evidence‐based knowledge and practical experience generated in three steps. (1) Experts from 8 wet grassland landscapes in northern Europe's west and east mapped factors linked to patterns and processes, and management and governance, in social‐ecological systems that affect states and trends of wet grasslands as green infrastructures for wader birds. (2) To understand wader conservation problems and their dynamic in wet grassland landscapes, and to identify key issues for successful conservation, we applied group modeling using causal loop diagram mapping. (3) Validation was made using the historic development in two additional wet grassland landscapes. Wader conservation was dependent on ten dynamically interacting ecological and social system factors as leverage points for management. Re‐wetting and grazing were common drivers for the ecological and social system, and long‐term economic support for securing farmers’ interest in wader bird conservation. Financial public incentives at higher levels of governance of wetland management are needed to stimulate private income loops. Systems analysis based on contrasting landscape case studies in space and over time can support (1) understanding of complex interactions in social‐ecological systems, (2) collaborative learning in individual wet grassland landscapes, and (3) formulation of priorities for conservation, management, and restoration. We used evidence‐based knowledge and practical experience generated in three steps. (1) Experts from 8 wet grassland landscapes mapped factors that affect states and trends of wet grasslands as green infrastructures for wader birds. (2) We then applied group modelling using causal loop diagram mapping. (3) Validation was made using the historic development in two additional wet grassland landscapes.
The successful conservation of bird species relies upon our understanding of their habitat use and requirements. In the coming decades the importance of such knowledge will only grow as climate change, the development of new energy sources and the needs of a growing human population intensify the, already significant, pressure on the habitats that birds depend on. Drawing on valuable recent advances in our understanding of bird-habitat relationships, this book provides the first major review of avian habitat selection in over twenty years. It offers a synthesis of concepts, patterns and issues that will interest students, researchers and conservation practitioners. Spatial scales ranging from landscape to habitat patch are covered, and examples of responses to habitat change are examined. European landscapes are the main focus, but the book has far wider significance to similar habitats worldwide, with examples and relevant material also drawn from North America and Australia.
The successful conservation of bird species relies upon our understanding of their habitat use and requirements. In the coming decades the importance of such knowledge will only grow as climate change, the development of new energy sources and the needs of a growing human population intensify the, already significant, pressure on the habitats that birds depend on. Drawing on valuable recent advances in our understanding of bird-habitat relationships, this book provides the first major review of avian habitat selection in over twenty years. It offers a synthesis of concepts, patterns and issues that will interest students, researchers and conservation practitioners. Spatial scales ranging from landscape to habitat patch are covered, and examples of responses to habitat change are examined. European landscapes are the main focus, but the book has far wider significance to similar habitats worldwide, with examples and relevant material also drawn from North America and Australia.
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The bar-tailed godwit (Limosa lapponica) and the black-tailed godwit (Limosa limosa) are two migratory shorebird species that spend the winter on the French Atlantic coast, before to reach regions further north for breeding. These two species share great phylogenetic proximity, and great morphological similarities inherited from a common ancestor from which they recently diverged. In such “closely-related” species, although identical responses are generally observed facing the same environmental conditions, the existence of unique niche properties and specific ecological needs have already been described. It is the case in bar-tailed and black-tailed godwits, which share the same wintering areas, but have a distinct reproduction distribution, breeding respectively in northern Eurasia and Alaska, and from Iceland to eastern Siberia. In France, we mainly observe the subspecies L. lapponica lapponica for bar-tailed godwit, and the subspecies L. limosa islandica for black-tailed godwit, which are present throughout the wintering period (August-April). The subspecies L. lapponica taymyrensis and L. limosa limosa are only present during the migration periods (February-March and August-October). In winter, L. l. lapponica and L. l. islandica mainly use mudflat ecosystems, on which they depend for feeding, as well as marine and coastal marshes, for roosting. Thus, in the Pertuis Charentais (France), they use the same wintering sites and the same functional areas, but exhibit distinct food preferences with a diet dominated by polychaetes worms for the bar-tailed godwit, and bivalves (eg Macoma balthica) and seagrass rhizomes (Zostera noltei) for the black-tailed godwit. Beyond this knowledge, this thesis aims to describe and compare the winter survival strategies of these two species, and especially their spatio-temporal use of habitats. The recent miniaturization of GPS tracking loggers has enabled us to equip individuals of both species to access to their daily and seasonal movements. Such an approach can significantly help to improve our knowledge on the biology of these birds, their dependence on coastal habitats and their link with protected areas / nature reserves. More specifically, we aim to explore the resources selection (prey and habitats) of the two godwit species, in relation to the use of rare roost sites mainly located in nature reserves. Precisely identify birds feeding areas, using GPS position data, allows sampling of potential benthic macrofauna prey, in order to estimate the energy quality of feeding patches and to describe available habitats. In addition, the analysis of bird’s activity on a fine spatial and temporal scale also allows exploring their adaptation to the nycthemeral periodicities, crossed with the use of protected and unprotected areas. Finally, since these birds exhibit a strong sexual dimorphism, it appears interesting to explore the existence of sexual segregation in terms of winter survival strategy. More generally, it is possible to investigate the differences between individuals, or their interactions during feeding in order to test affinities between birds in a gregarious species such as the black-tailed godwit. This work thus provides new key knowledge on the wintering survival strategies of the bar-tailed and the black-tailed godwits, and particularly on their use, in space and time, of different habitats. The results obtained underline both intraspecific and interspecific differences may exist in these two very similar species, which should be considered in future management and conservation measures.
Chick survival and breeding success of Black-tailed Godwits was studied in nine grassland sites (one site two years) in the central and western parts of The Netherlands between 1997 and 2000. Sites were used for modern dairy farming, but measures aimed at conservation of meadowbirds (postponed mowing, marking of nests and sparing them during mowing and grazing) were applied in (parts of) all of them. Nest success was calculated from daily survival rates. Chick survival was determined in 62 broods of which one of the parents was radio-tagged. Both parents stayed with their brood until about a week after fledging. Whereafter the female usually left a few days before the male. Based on birds that lost their clutch after being tagged, renesting rate after clutch loss was estimated at 100% in one site and 50% in the others. Renesting rate declined in the course of the spring, with no replacement clutches produced after late May. For the ten sites/years, the average proportion of nests in which 1 egg hatched was 54%, with a mean of 3.3 chicks hatched per successful nest. On average 26% of these survived to fledging (24 days), giving a mean of 0.56 young fledged per breeding pair (Tab. 2). In half to two-thirds of all 12 studies in Dutch agricultural grasslands to date, breeding success was lower than the 0.5-0.7 young/pair required for a stable population based on published mortality estimates. This implies insufficient breeding success as a cause of the 33% decline in breeding numbers observed in The Netherlands in the past ten years. Variation between our study sites/years, as well as very limited data from nature reserves (Tab. 3), suggest that chick survival and breeding success increase with the proportion of grassland mown late (after 31 May). We conclude that 'agricultural nature management schemes' can only safeguard a self-sustaining Black-tailed Godwit population on farmland when practical measures are applied at a larger scale, or more effectively, than at present.
The typical traditional Dutch grassland polder is a flat, open space, cut into squares by a maze of ditches and canals. It has a high water table and sometimes even winter inundations, hence no trees or buildings, which are found along the edges. Owing to a rare combination of soil, climate, hydrology, and management, these moist but fertile artificial prairies hold high densities (up to over 100 pairs/ km2) of six species of shorebirds, known as 'meadow birds.' This situation is now being changed with improved drainage, increased fertilization, earlier mowing, and higher cattle densities. Meadow-bird reserves can be recreated by imitating traditional methods and by keeping high water tables using dams and sluices. Meadow-bird management can be encouraged, for example, by financial compensation to private farmers for late mowing. Technically, we know how our meadow-bird populations can be preserved and managed; keeping them is mostly a political and financial matter. Despite some examples of very successful meadow reserves, Dutch meadow-bird populations are steadily declining.
Meadow bird agreements are the most important Dutch agri-environment schemes, both in terms of uptake and of aim. Meadow bird agreements postpone the first agricultural activities on grassland thus reducing egg and chick mortality due to mowing or grazing. We investigated the conservation effects of meadow bird agreements by analysing settlement densities of meadow birds on 34 fields in 1989, 1992 and 1995 in the province of Zeeland, The Netherlands. We compared territory numbers on fields with meadow bird agreements with paired nearby control fields that were conventionally managed. In 1995, the number of territories of black-tailed godwit (Limosa limosa), lapwing (Vanellus vanellus) and the total number of meadow birds were significantly higher on fields with conservation management. These differences were partly caused by the higher quality (i.e. higher groundwater level) of fields with meadow bird agreements. Population trends were similar on fields with and without meadow bird agreements and the observed difference in settlement density in 1995 was already present in 1989. Furthermore the effectiveness of the scheme did not increase with time. Thus we found no conclusive evidence that the conservation measures themselves did result in higher territory numbers. Currently, we do not have sufficient ecological and behavioural knowledge of meadow birds to explain why the higher reproductive success does not result in higher settlement densities.
The following critiques express the opinions of the individual evaluators regarding the strengths, weaknesses, and value of the books they review. As such, the appraisals are subjective assessments and do not necessarily reflect the opinions of the editors or any official policy of the American Ornithologists' Union.
Iceland is responsible for many internationally important populations of breeding bird species, yet very little is currently known about how these species use the habitats available to them. Lowland areas of Iceland, in particular, have undergone significant landscape changes over the last century, such as widespread drainage of wetlands and conversion to agriculture, changes in grazing pressure and recently, extensive afforestation. The impact of these changes on breeding bird species will depend on the relative importance of different habitats for each species, and the threats facing those habitats. Here we report the results of a large-scale survey of the factors influencing patterns of habitat selection of eight populations of Charadriiform bird species throughout lowland Iceland; oystercatcher Haematopus ostralegus, golden plover Pluvialis apricaria, dunlin Calidris alpina, snipe Gallinago gallinago, whimbrel Numenius phaeopus, black-tailed godwit Limosa limosa, redshank Tringa totanus and arctic skua Stercorarius parasiticus. Ordination analyses and multiple logistic regression models are constructed to explore the components of habitats that influence the distribution of these species. Five of the eight species analysed showed significant preferences for lowland wetland habitats and four significantly selected areas containing wet features such as pools and high water tables. These results allow us to identify future conflicts in land use that are likely to result from government-supported large-scale afforestation of lowland areas and hydro-electric developments.
Tréca, B 1994. The diet of Ruffs and Blacktailed Godwits in Senegal. Ostrich 65: 256–263. A study of the diet of Blacktailed Godwits Limosa limosa and Ruffs Philomachus pugnax by direct examination of stomach contents emphasizes the importance of rice, which accounted for over 80% of the items eaten. Rice was available at planting time in July-August and after the harvest in November-December. Thus fat deposition for migration, between January and April-May, is based on a rice diet (cultivated or wild rice). Very little animal matter was eaten. The choice of feeding ground will govern food choice among the available food. Birds which have eaten most are those which have found their preferred food.
Buffer effects occur when sites vary in quality and fluctuations in population size are mirrored by large changes in animal numbers in poor-quality sites but only small changes in good-quality sites. Hence, the poor sites 'buffer' the good sites, a mechanism that can potentially drive population regulation if there are demographic costs of inhabiting poor sites. Here we show that for a migratory bird this process can apply on a country-wide scale with consequences for both survival and timing of arrival on the breeding grounds (an indicator of reproductive success). The Icelandic population of the black-tailed godwit, Limosa limosa islandica, wintering in Britain has increased fourfold since the 1970s (ref. 5) but rates of change within individual estuaries have varied from zero to sixfold increases. In accordance with the buffer effect, rates of increase are greater on estuaries with low initial numbers, and godwits on these sites have lower prey-intake rates, lower survival rates and arrive later in Iceland than godwits on sites with stable populations. The buffer effect can therefore be a major process influencing large-scale population regulation of migratory species.