ArticlePDF Available

Abstract and Figures

Fish may significantly affect habitat use by birds, either as their prey or as competitors. Fish communities are often distinctly size-structured, but the consequences for waterbird assemblages remain poorly understood. We examined the effects of size structure of common carp (Cyprinus carpio) cohorts together with other biotic and abiotic pond characteristics on the distribution of breeding waterbirds in a seminatural system of monocultured ponds, where three fish age classes were separately stocked. Fish age corresponded to a distinct fish size gradient. Fish age and total biomass, macroinvertebrate and amphibian abundance, and emergent vegetation best explained the differences in bird density between ponds. Abundance of animal prey other than fish (aquatic macroinvertebrates and larval amphibians) decreased with increasing carp age in the ponds. Densities of ducks and smaller grebes were strongly negatively associated with fish age/size gradient. The largest of the grebes, the piscivorous great crested grebe (Podiceps cristatus), was the only species that preferred ponds with medium-sized fish and was positively associated with total fish biomass. Habitat selection by bitterns and most rallids was instead strongly influenced by the relative amount of emergent vegetation cover in the ponds. Our results show that fish size structure may be an important cue for breeding habitat choice and a factor affording an opportunity for niche diversification in avian communities.
Content may be subject to copyright.
ORIGINAL PAPER
Habitat selection by breeding waterbirds at ponds
with size-structured fish populations
Janusz Kloskowski &Marek Nieoczym &Marcin Polak &
Piotr Pitucha
Received: 1 April 2010 /Revised: 22 May 2010 /Accepted: 24 May 2010 /Published online: 8 June 2010
#Springer-Verlag 2010
Abstract Fish may significantly affect habitat use by birds,
either as their prey or as competitors. Fish communities are
often distinctly size-structured, but the consequences for
waterbird assemblages remain poorly understood. We
examined the effects of size structure of common carp
(Cyprinus carpio) cohorts together with other biotic and
abiotic pond characteristics on the distribution of breeding
waterbirds in a seminatural system of monocultured ponds,
where three fish age classes were separately stocked. Fish
age corresponded to a distinct fish size gradient. Fish age
and total biomass, macroinvertebrate and amphibian abun-
dance, and emergent vegetation best explained the differ-
ences in bird density between ponds. Abundance of animal
prey other than fish (aquatic macroinvertebrates and larval
amphibians) decreased with increasing carp age in the
ponds. Densities of ducks and smaller grebes were strongly
negatively associated with fish age/size gradient. The
largest of the grebes, the piscivorous great crested grebe
(Podiceps cristatus), was the only species that preferred
ponds with medium-sized fish and was positively associat-
ed with total fish biomass. Habitat selection by bitterns and
most rallids was instead strongly influenced by the relative
amount of emergent vegetation cover in the ponds. Our
results show that fish size structure may be an important
cue for breeding habitat choice and a factor affording an
opportunity for niche diversification in avian communities.
Keywords Common carp .Distant competition .
Habitat selection .Size-structured interactions .
Waterbird assemblages
Introduction
The influence of ecological interactions between distantly
related taxa upon patterns of habitat use is one of the
focuses of ecological and evolutionary research (Levins
1979; Safina and Burger 1985; Englund et al. 1992).
Interactions between fish and bird populations are known to
range from predation to competition. Fish-eating birds
profit from increases in fish populations (Lammens 1999),
while negative effects of fish on waterbird distribution have
been documented and attributed to exploitative competition
(Eriksson 1979; Eadie and Keast 1982; Hurlbert et al. 1986;
van Eerden et al. 1993). Fish communities frequently
exhibit a distinct size structure due either to external
disturbances promoting dominance of single size cohorts
or to inter- and intraspecific trophic interactions between
cohorts (e.g., Tonn and Magnuson 1982; Persson 1988;
McParland and Paszkowski 2006). The variability in size
structure of fish populations may be expected to affect the
habitat choice and reproductive success of many water-
birds, depending on the species involved. Larger fish can be
more profitable prey for avian predators, but on the other
hand, fish susceptibility to predation may decrease with
J. Kloskowski (*):M. Polak
Department of Nature Conservation, Institute of Biology,
Maria Curie-Skłodowska University,
Akademicka 19,
20-033 Lublin, Poland
e-mail: januszkl@hektor.umcs.lublin.pl
M. Nieoczym
Department of Zoology, University of Life Sciences,
Akademicka 13,
20-950 Lublin, Poland
P. Pitucha
Inspectorate for Environmental Protection in Lublin,
Obywatelska 13,
20-092 Lublin, Poland
Naturwissenschaften (2010) 97:673682
DOI 10.1007/s00114-010-0684-9
growth (Moser 1986). As most fishes are size-limited in
feeding, in species with large terminal body sizes, the
ability to compete with birds may increase over ontogeny.
Fish may also affect the environmental context of inter-
actions with birds, e.g., via bioturbation (Lammens 1999;
Zambrano et al. 2001), and their potential for habitat
alteration can be size dependent (Driver et al. 2005).
However, little is known of size-structured fishbird
interactions (but see Paszkowski and Tonn 2000), as most
studies have addressed avian habitat selection in relation to
the presence/absence of fish (Eriksson 1979; Hurlbert et al.
1986; Allen et al. 2007) or along a fish density gradient
(Hill et al. 1987; Haas et al. 2007). Since patterns of fish
size structure are predictable in many natural and human-
managed systems (Tonn and Magnuson 1982; Holmgren
and Appelberg 2000), elucidation of size-dependent effects
of fish on birds may be necessary to understand the
functioning of these systems and provide practical solutions
for waterbird conservation strategies.
The aim of this study was to examine how size structure
of fish influences assemblage composition of pond-
breeding waterbirds and what role fish size plays in
determining distribution of waterbirds relative to other
biological and habitat variables. We chose to work on the
common carp (Cyprinus carpio) because carp populations
frequently form strong year classes and consequently
distinct size structure; predation by piscivorous birds is
usually limited to the first- or second-summer cohorts
(Mraz and Cooper 1957; Moser 1986). Moreover, carp
commonly play a key role in structuring aquatic commu-
nities and can negatively affect food resources of waterfowl
(Crivelli 1983; Haas et al. 2007; Bajer et al. 2009). We
predicted that fish size structure would have a strong
influence on habitat selection by some waterbirds, while on
the other hand, we expected certain pond habitat features,
such as emergent vegetation, to affect distribution of
individual bird species among ponds. Therefore, we studied
patterns of habitat selection by waterbirds at the community
and individual species level, taking into account biotic and
abiotic habitat properties that might influence those
patterns, along a gradient of three carp age (size) classes:
young-of-the-year cohorts, 1-year-old fish, and 2-year-old
fish. The study system consisted of open carp ponds where
fish age cohorts were stocked separately and the age of the
cohorts was irregularly rotated between years. As it is
difficult to manipulate habitat choice of birds exploiting
spatially extensive ranges, seminatural systems such as
monoculture pond fisheries offer a valuable alternative
(Suter 1991; Haas et al. 2007) providing conditions for
natural experimentssensu Diamond (1986). The clear-cut
size distribution of fish age cohorts among ponds provided
an excellent opportunity to examine size-structured fish
bird interactions using a whole-system approach.
Methods
Study system
The study was conducted in cooperation with the local
fisheries staff at extensively managed carp ponds in
southeastern Poland. During two breeding seasons, in
2002 and 2004, 39 and 46 ponds were surveyed. The
ponds belonged to five pond complexes (in total 651
682 ha of water surface area) situated 1060 km apart. The
eutrophic, typically monoculture ponds in SE Poland are
readily used by breeding birds and are acknowledged
strongholds for waterfowl (Grimmet and Jones 1989).
The privately administered ponds formerly belonged to a
single state-owned fisheries organization; hence, manage-
ment practices were alike for all study sites and all carp
stocks originated from the same hatchery. Three fish age
classes were stocked in separate growing-on ponds, and a
well-defined size gradient of fish cohorts was created.
Before introduction into the ponds, all carp were weighed
to establish the total stock biomass in each pond, and a
large sample of fish was weighed to determine mean
individual biomass. Stocking biomasses were on average
similar in 1+ and 2+ ponds (225±SE 29 vs 224 ± 28 kg/ha)
but were much larger than in 0+ ponds (Table 1), where
carp attained total biomass >50 kg ha only in late June.
During the spring stocking period (AprilMay), young-
of-the-year (0+; small-sized) carp were stocked at an
individual weight of 1.53.0 mg, to reach 58g(7to
8 cm in length) within ca. 2 months; 1+ (medium-sized)
carp weighed ca. 3050 g and 2+ (large-sized) carp ca.
150250 g. Due to substantial differences in fish size
between year cohorts under pond culture conditions, carp
age and the age-specific size range are considered inter-
changeable here. Potential carry-over effects of cohort
distribution (i.e., the influence of events in pond ecosys-
tems in past breeding seasons on the current habitat choice
of birds) were minimized because in most of the ponds, the
age of the carp stocks was rotated between years (albeit
irregularly, each year in ca. 3060% of the studied ponds,
depending on the fish farm's current supply of the given
year-class of fish). Age cohorts were alternated either by
stocking different age classes in rotation in subsequent
years or leaving cohorts in the same ponds for 2 years. Carp
densities were within the ranges found in natural systems
(Table 1; Crivelli 1983; Panek 1987). Other fish occurred in
the ponds (small wild-grown and supplemental species,
mainly bleak (Leucaspius delineatus), wels (Silurus glanis),
or pike (Esox lucius)), but carp were overwhelmingly
dominant (9598% of the total fish biomass per pond; M.
Filipiak and M. Sagan, personal communication). The
proportion of small fish that invaded the ponds despite the
screens at the water inlets was typically visually assessed
674 Naturwissenschaften (2010) 97:673682
by fish farmers during draining operations because wild
fish were only occasionally collected. However, a few
ponds known to develop noticeable proportions of wild-
grown fish, usually following serious carp mortality
episodes, were excluded from the analyses.
The ponds were similar in depth (mean values 0.7
1.3 m) but differed in emergent aquatic vegetation cover
along the pond margins (mainly Typha angustifolia and
Phragmites australis) and in surface area (Table 1; see
Kloskowski 2009 for more details on the study system).
Bird surveys
Waterbirds were counted between April and July at ca. 10-
day intervals (each pond was visited 12 times during the
season). The round count method of Koskimies and
Väisänen (1991) was used. We walked around the ponds
and counted birds using binoculars and scopes. We counted
only nonpasserine birds classified as pond breeders (nesting
on ponds or pond levees) and feeding at or beneath the
surface of the water. We used playback of species' calls
(Bibby et al. 2000) to detect territories of little grebe
(Tachybaptus ruficollis) and of rallids other than coot
(Fulica atra). The vocalizations were broadcast using a
tape recorder early in the morning and after sunset.
Numbers of breeding pairs (breeding territories) were
estimated following the method of Koskimies and Väisänen
(1991), with some modifications for pond conditions
(Ranoszek 1983). Analyses were restricted to species
occurring in >5% of the ponds: little grebe, great crested
grebe (Podiceps cristatus), red-necked grebe (Podiceps
grisegena), little bittern (Ixobrychus minutus), great bittern
(Botaurus stellaris), mute swan (Cygnus olor), mallard
(Anas platyrhynchos), garganey (Anas querquedula), po-
chard (Aythya ferina), tufted duck (Aythya fuligula), water
rail (Rallus aquaticus), little crake (Porzana parva),
moorhen (Gallinula chloropus), and coot. Where necessary,
breeding species data were converted to densities (birds/10 ha).
Fish and habitat variables
Data on pond size, carp age, and standing biomass in
individual ponds were provided by the staff of the local
fisheries. Ponds were also classified by hydroperiod (ponds
winteringvs flooded in spring). At each pond, a number
of variables were measured for use in analyses predicting
the community structure and responses of individual bird
species. Relative abundances of amphibian larvae and
aquatic invertebrates were estimated from pond surveys
using funnel activity traps. In 2002 and 2004, the study
sites were visited in random order from 27 April to 11 May
and between 19 June and 4 July to collect the spring and
summer fauna. The traps (modeled after Murkin et al. 1983;
Griffiths 1985) were cylindrical with a 23-mm aperture at
the narrow end of the funnel. Trapping is a reliable method
of estimating the availability of nonfish prey taken by
Table 1 Pond habitat variables (mean and range) sampled in 2002 and 2004, selected as potential predictors of breeding bird densities
Variable Description Mean (range)
Pond area Water surface area (ha) 4.8 (0.826)
Fish age 0+, 1+, 2+carp cohorts 0+, 51%; 1+, 29%; 2+, 20%
Fish standing biomass Total carp biomass (kg/ha) during the spring
stocking period (Aprilearly May)
0+, negligible at stocking
(ca. 1 kg ha); 1+, 225
(105501); 2+, 224 (176490)
Pond permanence Ponds that held or gathered water over winter
vs ponds which remained dry in winter and
were refilled in late March to early May (treated
as a categorical factor in the analyses)
Ponds wintering, 34%; flooded
in spring 76%
Amphibian abundance Relative wet weight (g/1 trap) 18.4 (074.8)
Macroinvertebrate abundance Relative dry weight (mg/1 trap) 0.82 (08.1)
Water transparency Secchi disk (26 cm diameter) depth (cm) 102.8 (30180)
Emergent pond vegetation Proportion of pond surface area covered by emergent
aquatic plants
24.9 (2.577)
Shoreline development The ratio of the pond perimeter to the doubled square
root of the product of πand the pond surface area
1.5 (02.9)
Urbanized landscape Proportion of the shoreline adjacent to urbanized
habitat, i.e., roads and human settlements
0.2 (01.0)
Forest landscape Proportion of the shoreline covered by forest 0.1 (01.0)
Agricultural landscape Proportion of the shoreline adjacent to arable fields or pasture 0.2 (00.9)
Pond connectivity Proportion of the shoreline adjacent to other ponds 0.5 (01.0)
For fish age and pond permanence, the percentage of ponds studied belonging to the given category is presented instead
Naturwissenschaften (2010) 97:673682 675
waterfowl (Elmberg et al. 1994). Ten traps were set in each
pond for 48 h (see Kloskowski 2009 for details of the
trapping procedure). The traps were approximately evenly
distributed in open water areas close to emergent vegetation
in order to sample both habitats. Invertebrates 4mm
(hereafter macroinvertebrates) caught in the traps were
identified (typically to family or genus). For common taxa,
dry weights were predicted from lengthweight regressions
obtained after drying subsamples to stable weight at 5060°C.
Macroinvertebrates from rare taxa were collected and
weighed after drying. Any tadpoles caught were wet-
weighed in the field after drip drying. During each
sampling visit, Secchi transparency was measured at the
deepest parts of the ponds. The two sampling sessions
spanned the time period used to establish numbers of
breeding birds (Ranoszek 1983; Koskimies and Väisänen
1991), and since data collected at 2-week intervals from a
smaller subset of ponds indicated that the variables
measured (amphibian and macroinvertebrate abundance,
water transparency) either remained stable or showed
monotonic increase over late Aprilend of June (M.
Nieoczym and J. Kloskowski, unpublished data), we used
averages of the two catches/measurements in the analyses,
on the assumption that they represented the variability
between the ponds over the study period.
During the JuneJuly 2002 sampling sessions, water
chemistry data (electrical conductivity, pH, concentrations of
dissolved oxygen, organic carbon, ammonia nitrogen NH
4
-N,
nitrate nitrogen NO
3
-N, and available phosphate PO
4
-P)
were sampled (see Kloskowski 2009 for a detailed descrip-
tion of the methods). However, in the preliminary analyses
(see Data analysissection), which included only the 2002
data, none of the chemical variables had a significant effect
on the composition of bird assemblages or on individual
species. Therefore, the analyses were conducted on data
from both 2002 and 2004, omitting the chemical variables.
Emergent vegetation cover and the shoreline develop-
ment index (Lind 1985) were determined by digitization
from groundproofed (a planimeter was used) aerial photos.
To describe the surrounding landscape characteristics for
each pond, we estimated the proportion of the shoreline
adjacent to urbanized habitat, to forest patches, to arable
fields/pasture, and to other ponds. We restricted the
landscape scale to a ca. 2030 m buffer because all study
sites were situated in agricultural landscape, with small
patches of woodland (see Table 1for a complete list of
variables collected in both 2002 and 2004).
Data analysis
Canonical correspondence analysis (CCA; CANOCO 4.5;
ter Braak and Šmilauer 2002) was used to determine the
variables that best predicted the composition of the pond-
breeding bird community. CCA is a direct gradient analysis
that iteratively develops an ordination of species and
sampling sites, combined with multiple regression on a
series of environmental gradients. A set of environmental
variables is reduced to a few orthogonal axes as composite
environmental gradients structuring species distribution
patterns. The significance of the relation of each environ-
mental variable to the bird data was determined by the
magnitude of the additional variation the variable explained
(conditional effects). Stepwise forward selection was
used to include significant variables (P<0.05) in the model.
The significance of the first canonical axis and of all
canonical axes together was tested by the distribution-free
Monte Carlo simulation (999 permutations). Multicollinear-
ity of the habitat variables was not excessive (variance
inflation factor (VIF) <7; VIF range for variables chosen by
the stepwise forward procedure 1.162.32). To partial out
the effects of the year of sampling and study locations
(pond complexes) from the model, they were included in
the ordination as categorical (dummy) covariables. When a
pond was sampled in both study years, we randomly
selected 1 year to be excluded from the model.
Although CCA provides information on the habitat
associations of individual species, its main goal is to
determine the relative effects of environmental variables
on the bird community as a whole. Therefore, generalized
linear mixed models (GLMMs) with Poisson distribution
and logarithmic link (GenStat v. 11.0) were used to identify
the habitat conditions most important in determining the
densities of individual bird species and bird species
richness (the number of avian taxa recorded per pond) at
the ponds. For bitterns, mute swan, little crake, and water
rail, typically represented by no more than one breeding
pair (calling individual) per pond due either to strong
territorial behavior or to relatively low overall abundance,
we considered presence/absence data in binomial models
with logit link to be more appropriate. Also, in two species
that are known to be involved in strong agonistic
interactions with sympatric larger-bodied species, interspe-
cific interactions were considered: great crested grebe
presence was added to the models of red-necked grebe
densities as an explanatory categorical variable and coot
presence to the models of moorhen (Cramp 1985; Fjeldså
2004). The other advantage of the GLMMs was that data
from all ponds surveyed in 2002 and 2004 were used,
including ponds sampled twice. With regard to the close
proximity distribution of the ponds clustered in pond
complexes, we assumed spatial autocorrelation between
data points from the same pond complexes. Therefore, the
random model included year and pond identity nested
within pond complex to account for lack of temporal and
spatial independence of observations. We used a step-down
procedure to select the final models. Starting with a full
676 Naturwissenschaften (2010) 97:673682
model, the densities of each species were analyzed
including all variables used in the CCA as main effects
and two-way interactions. A quadratic term (fish age
squared) was added to account for potential nonlinear
effects of the fish age gradient. To prevent multicollinearity,
the quadratic term was centered by subtracting the mean of
the variable from each case's value before squaring it. We
used a correlation matrix to test candidate variables for
multicollinearity, and significance of predictor variables
with pair-wise correlation coefficients >0.3 was tested in
our models omitting the correlated variable, i.e., alternative
models were constructed. We progressively simplified the
model by eliminating first interactions and then main terms
that were the furthest from statistical significance. To verify
that significant terms had not been wrongly excluded, each
dropped term was then refitted to the minimal model. Wald
tests were used to assess significance of fixed terms. Fish
age was fitted as a continuous variable in the models;
however, for presentation of the observed patterns, carp age
classes were treated as a nominal term with three levels so
that means and SE could be calculated.
We did not apply the Bonferroni correction when multiple
tests on different response variables (species) addressed the
same hypothesis (Moran 2003). Data were log (x+1) or
arcsin-transformed to improve normality before GLMM
analyses. Data were not transformed for CCA.
Results
The five environmental variables included by the CCA
forward selection as best differentiating habitat preferences
of waterbirds were macroinvertebrate abundance (condi-
tional importance λ
a
=0.12, F=5.17, P=0.002), fish age (as
an ordinal trend; λ
a
=0.11, F=4.78, P=0.002), fish biomass
(λ
a
=0.10, F=4.47, P=0.008), amphibian abundance (λ
a
=
0.06, F=3.25, P=0.014), and emergent vegetation cover
(λ
a
=0.08, F=4.12, P=0.002; Fig. 1). Permutation tests on
the trace value (0.703; F=3.219, P=0.001) and on the value
of axis 1 (eigenvalue=0.234; F=8.95, P=0.001) indicated
that the variables included in the model explained a
significant amount of the variation in the species data. Of
the variables selected by the CCA models, significant
correlations (at P<0.05) were found between fish age and
biomass (r=0.6353); both these variables were negatively
related to macroinvertebrate abundance in activity traps
(r=0.2408 and r=0.2707). Abundance of larval amphib-
ians was negatively correlated with fish age (r=0.2265;
GLMM means of relative amphibian abundance in ponds
with different-aged carp are presented in Table 2), but
the relationship with fish biomass was not significant
(r=0.1580). Also, amphibian abundance was associated
with emergent vegetation (r=0.2994).
The inertia in the species data after fitting the covariables
was 1.776. Of this, the first axis explained 12% and the
second axis 6.3%. The canonical eigenvalues accounted
together for 26.6% of the total variance. Correlation
coefficients indicated that axis 1 of the CCA reflected
trends across richly vegetated habitats (r=0.5783) to open
water habitats and those of increasing aquatic macro-
invertebrate abundance (r=0.5944). Axis 2 was largely
defined by the gradient of fish age (r=0.7272) and fish
biomass (r=0.8889).
Individual ordination scores for bird species indicated
that breeding habitat was selected with regard to food
(macroinvertebrate or amphibian abundance, fish age, total
fish biomass) and/or the proportion of emergent vegetation
cover (Fig. 1). Tufted duck (r=0.4942, P< 0.001) and
mallard (r=0.3266, P<0.005) densities were most strongly
correlated with macroinvertebrate relative abundance. The
direction of the environmental vectors revealed that the
presence of larger fish was negatively correlated with larval
amphibian densities. Little grebe densities that correlated
best with amphibian abundance (r=0.3772, P< 0.001) were
also negatively associated with fish age (r=0.4337, P<
0.001) and fish biomass (r=0.3164, P<0.004). Great
bittern and rallids (except moorhen) were associated with
abundant emergent vegetation (r0.34, all P<0.003). The
most common species in terms of overall occurrence,
mallard (overall pond occupancy 89.4%) and coot
(87.1%), but also mute swan (38.8%), tended to be
clustered around the origin of the ordination, i.e., they
were the most habitat generalist species.
Fig. 1 Results of CCA on avian communities and environmental
variables in 74 carp ponds sampled in 2002 and 2004
Naturwissenschaften (2010) 97:673682 677
Although some associations determined by CCA were
not detected by the GLMMs, the GLMMs confirmed that
habitat selection by individual species was typically
influenced by either a food-related variable (most frequent-
ly the age of the fish in the pond; Fig. 2) or emergent
vegetation cover (Table 3). Little grebe was the only species
whose habitat selection depended on both fish age and the
vegetation cover of the pond. In the case of grebes, little
grebe preferred ponds with the youngest cohorts, red-
necked grebe occurred in both 0+ and 1+ but was absent
from 2+ ponds, and great crested grebe achieved the
relatively highest breeding densities on 1+ ponds (Table 3;
Fig. 2). No species was found to be positively associated
with 2+ fish. Total fish biomass was correlated with carp
age, but when included in the null models omitting carp
age, it was positively related only to the densities of great
crested grebe and pochard (Table 3). Pond area and water
transparency were not selected by the CCA procedure (λ
a
<
0.06, both P>0.1) but were found significant for individual
distribution patterns of some species by the GLMM. Water
transparency was positively related to densities of coot, red-
necked grebe, and great crested grebe. As indicated by the
CCA correlation matrix, Secchi depth decreased with
increasing fish age and total biomass (r=0.2969 and
r=0.3034; Table 2). Also, GLMMs demonstrated the
potential importance of interspecific interactions within
waterbird guilds: Densities of red-necked grebe were
positively related to great crested grebe presence, while
moorhen showed a negative association with coot (Table 3).
Total species richness was negatively related to fish age
(Wald χ
2
=4.42, df=1, P=0.0239) and positively correlated
with pond size and the proportion of emergent vegetation
(χ
2
17.0, df=1, both P<0.001).
Discussion
Our results show that waterbirds used two types of general
cues for breeding habitat selection and two groups of
species could be distinguished accordingly, although the
suites of preferred habitat attributes overlapped between the
groups. Densities of grebes and ducks were related to food
availability (fish age and density, invertebrate or amphibian
abundance; cf. Nummi et al. 1994; Haas et al. 2007).
Bitterns and rallids were positively related to the amount of
emergent vegetation, which might function both as shelter
from predators and as a specific feeding habitat for some
species (Jenkins and Ormerod 2002; Gilbert et al. 2003),
while they were generally not correlated with the size
structure of the fish community. The species studied have
varying ability to move their young to another pond
Fig. 2 Breeding densities (pairs or calling males per 10 ha) of grebes,
ducks (a), bitterns, and rallids (b) in carp ponds stocked with different
age cohorts. 0+= young-of-the-year carp, 1+ = 1-year-old carp, 2+ = 2-
year-old carp. GLMM predicted means (+SE) are shown. Note that
GLMM statistics on bitterns and some rallids presented in Table 3are
derived from binomial models using species presence/absence data
(see text for more details). Superscripts denote significant differences.
Garganey was omitted because of its rare occurrence at ponds
Table 2 Effects of fish age/size structure on variables related to food availability for waterbirds (GLMM, normal error and identity link function)
Mean (SE) Wald χ
2
(df=2) P
0+ ponds
(N=37)
1+ ponds
(N=22)
2+ ponds
(N=15)
Amphibian abundance (g/1 trap; wet weight) 9.69
a
(2.76) 1.06
b
(0.61) 0.21
b
(0.15) 6.16 0.050
Macroinvertebrate abundance (mg/1 trap; dry weight) 0.78
a
(0.12) 0.33
b
(0.07) 0.27
b
(0.07) 14.47 <0.001
Water transparency (cm) 125.7
a
(5.6) 92.5
b
(7.2) 77.8
b
(6.6) 10.58 0.007
Unlike superscripts denote significant differences (2 standard errors of the difference=95% confidence limits)
678 Naturwissenschaften (2010) 97:673682
(reviewed in Elmberg et al. 1994); however, we assume that
even in the mobilespecies (particularly dabbling ducks)
the choice of nesting habitat is critical for breeding success
because chick mortality is the highest in the early
posthatching period when moving the brood seems most
risky (Hill et al. 1987; reviewed by Sargeant and Raveling
1992). In great crested grebe and red-necked grebe, the
preference for the early flooded ponds is probably related to
grebesinability to walk (Fjeldså 2004). After settling on
ponds that are already filled, the early breeders cannot
choose a different territory until the young have fledged,
unless the clutch/brood fails.
The age/size of carp in the ponds significantly influenced
densities of macroinvertebrates and larval amphibians.
Nonfish prey of waterfowl can be heavily suppressed by
fish predation (Eriksson 1979; Mallory et al. 1994). These
effects may substantially depend on individual fish size due
to fish capability of foraging on progressively larger prey
over ontogeny (Persson 1988; Penttinen and Holopainen
1992). The size-dependent potential for predation on or
competition with fish was apparently decisive for habitat
choice in the grebe-duckassemblage. Young ducks and
little and red-necked grebes feed heavily on macroinverte-
brates and larval amphibians (Bandorf 1970; Hill et al.
1987; Kloskowski 2004). Therefore, breeding birds may
avoid resource competition by shunning ponds with large-
sized fish. The affinity to emergent vegetation among
grebes was in inverse order to body size. Little grebe and
red-necked grebe are well adapted for foraging both on
open water and within emergent vegetation (Bandorf 1970;
Table 3 GLMMs (fixed part) for the estimated breeding densities or presence/absence of individual species and avian species richness at the
ponds
Species Effect Estimate ± SE Wald χ
2
(df=1) P
Little grebe Fish age 0.748± 0.274 7.46 0.008
Emergent vegetation 3.265± 1.088 9.00 0.005
Amphibian abundance 0.436±0.203 4.60 0.036
Great crested grebe Pond area 0.965±0.299 10.44 0.002
Water transparency 0.986± 0.355 7.69 0.007
Fish squared age 1.468±0.341 18.56 <0.001
Pond permanence 1.276± 0.528 5.85 0.018
Fish biomass 0.195± 0.046 18.04 <0.001
Red-necked grebe Fish age 0.614±0.296 4.28 0.038
Water transparency 0.719± 0.373 3.74 0.05
Pond permanence 4.906± 1.494 8.48 0.004
Great crested grebe presence 1.616 ± 0.536 9.09 0.003
Little bitern Emergent vegetation 3.396± 1.501 5.12 0.027
Great bittern Emergent vegetation 5.500± 1.530 12.92 0.001
Pond area 1.374±0.435 9.95 0.003
Mute swan Pond area 0.678± 0.228 8.85 0.005
Mallard Fish age 0.344± 0.153 5.09 0.027
Pochard Fish age 0.644± 0.217 8.82 0.003
Tufted duck Fish age 0.781±0.309 6.38 0.013
Fish biomass 0.142±0.059 5.87 0.015
Water rail Emergent vegetation 12.090 ± 3.061 15.61 <0.001
Pond area 2.940±0.838 12.31 0.001
Little crake Emergent vegetation 8.477 ± 3.115 7.41 0.009
Pond area 2.062±0.888 5.39 0.024
Moorhen Shoreline development 1.920 ± 0.577 11.07 0.001
Coot presence 1.352± 0.463 8.54 0.005
Coot Water transparency 0.986± 0.211 8.68 0.004
Emergent vegetation 2.263± 1.065 4.52 0.037
Amphibian abundance 0.620 ± 0.120 5.97 0.017
Garganey was omitted because it occurred in only 7% of the ponds. For the sake of brevity, the reduced models resulting from stepwise backward
dropping of insignificant terms are presented. Statistics and Pvalue of significant terms were taken from the minimal models; in great crested
grebe and tufted duck, they were obtained by entering each of the intercorrelated variables into separate models
Naturwissenschaften (2010) 97:673682 679
Fjeldså 1982). Great crested grebes may be the least
dependent on emergent vegetation as they pursue prey
while diving in open water and nest even in very sparsely
vegetated places (Fjeldså 2004). Females of the duck
species studied can nest on pond shores or in sparse
vegetation stands and thus rely more on food abundance in
selecting a breeding habitat (see also Giles 1994; Nummi et
al. 1994). Total fish biomass was an important factor
structuring the avian community as a whole, but when
individual patterns of species distribution were analyzed, it
was associated only with great crested grebe and tufted
duck densities. The effects of fish size and total biomass are
difficult to separate in age-structured carp ponds because in
spring, the biomass of young-of-the-year fish, even when
stocked at high numerical densities, is naturally lower than
that of older stocks. Since exceeding a critical density
threshold is a prerequisite of carp impact on aquatic
community (Zambrano et al. 2001; Bajer et al. 2009),
density-dependent effects cannot be neglected. However,
notwithstanding that 1+ and 2+ fish were stocked at similar
levels of total biomass, densities of some bird species
differed significantly between 1+ and 2+ ponds, indicating
that the effect of carp size structure on these species was
stronger than that of density.
Benthivorous fish such as carp can impact birds by
elevating turbidity levels and disturbing submerged vege-
tation, which at high fish density induces an ecosystem shift
to a macrophyte-poor turbid state (Crivelli 1983; Lammens
1999; Zambrano et al. 2001). These effects may be related
to fish body size as well. Larger-sized benthivorous carp are
capable of digging deeper in a substratum (Lammens and
Hoogenboezem 1991) and create more turbidity via
sediment and phosphorus suspension than small fish
(Driver et al. 2005). The loss of macrophytes adversely
affects the density of waterfowl foraging on vegetation and its
associated invertebrates (cf. Hargeby et al. 1994). Elevated
turbidity levels restrict the foraging efficiency of visually
hunting avian predators (Cezilly 1992; Brenninkmeijer et al.
2002). However, even in the 2+ ponds (i.e., the ponds
holding the oldest and largest fish), the average Secchi depth
was still far from the estimated lower acceptable limit of ca.
40 cm for efficient great crested grebe predation on fish (van
Eerden et al. 1993). The negative effects of fish on
vegetation and water clarity can be delayed until summer
(cf. Meijer et al. 1990;Haasetal.2007), and breeding
waterbirds may not be seriously affected, at least during the
early breeding period. In carp ponds, the delay can be
explained by low water temperature and reduced fish feeding
activity in spring (Penttinen and Holopainen 1992; Richardson
and Whoriskey 1992). We observed blue-green algae blooms
in 1+ ponds only at the end of July and in August. Therefore,
we suggest that the negative effects of carp on waterbirds were
mainly driven by competition for food. Consequently, fish
species that feed in the water column and are capable of
attaining body size that allows exploitation of resources used
by waterfowl may have no less potential to influence habitat
suitability for birds than benthivorous fish (Eriksson 1979;
Hill et al. 1987).
Bitterns and rallids rely at least in large part on animal
diet, especially in the prefledging period, but only coot,
being the single species that commonly acquires prey by
diving (Cramp 1985), showed association with indices of
food availability. However, our trapping method is likely to
assess abundance of epibenthic and nektonic prey in open
water habitats or open water interspersed with emergent
vegetation stands, while some of the bird species dwelling
in emergent vegetation are adapted for gleaning prey from
emergent plants or gathering food on dry sites (Cramp
1985; Jenkins and Ormerod 2002). The piscivorous great
bittern is a food opportunist that forages chiefly within
dense stands of vegetation (Gilbert et al. 2003) and in pond
conditions takes small wild-grown fish rather than carp
(Polak 2007); thus, it may be independent of carp size
structure. Among rallids, only moorhen was not related to
emergent vegetation, but its distribution may be governed
by agonistic competition with the more dominant coot.
Moorhen is also strongly associated with terrestrial habitats
around the breeding pond (Cramp 1985).
To sum up, fish individual size and factors which interact
with size structure of fish populations, such as macro-
invertebrate and amphibian abundance, water transparency,
and pond permanence (Penttinen and Holopainen 1992;
Driver et al. 2005), can play an important role in shaping
distribution patterns of a significant part of the waterbird
community, while avian guilds strongly associated with
emergent vegetation were little responsive to variability in
both fish size and density. Size structure of fish populations
can also better explain niche diversification between some
bird species than the fish presence/absence dichotomy.
Waterfowl susceptible to competition from fish benefit from
avoiding water bodies containing fish (Eriksson 1979; Giles
1994), and our data suggest that ducks tend to avoid ponds
with larger fish in particular, presumably because they are
more effective competitors than small fish. Small- and
medium-sized piscivorous birds may prefer waters with rich
populations of small-bodied fish over both habitats without
fish and those dominated by large fish, i.e., invulnerable to
predation (Allen et al. 2007; but see Paszkowski and Tonn
2000). Larger-bodied piscivorous species, like great crested
grebe in the present study, are likely to select water bodies
with bigger fish, attempting to align their size-limited
predatory capacity with the better energetic return and
other advantages of larger prey (Moser 1986; van Eerden et
al. 1993; Paszkowski and Tonn 2000). In conditions of
distinct fish size structure, e.g., in northern temperate
shallow water bodies, where fish populations are regularly
680 Naturwissenschaften (2010) 97:673682
structured by winter hypoxia or drought years (Tonn and
Magnuson 1982; Holopainen and Hyvarinen 1985; Allen et
al. 2007), individual fish size can be more significant than
fish density for avian community composition. However, it
should be recognized that the interplay between relative
densities of fish size cohorts may be foremost in importance
in more speciose assemblages with a mixture of size classes.
From a management perspective, large, heavily vegetat-
ed water bodies with small-bodied fish populations are
likely to host the highest number of avian species (Elmberg
et al. 1994; Weller 1999; Paszkowski and Tonn 2000).
Habitats managed for breeding ducks and the smaller grebe
species should harbor only small-bodied (young) fish or
remain fishless (see also Giles 1994). However, water
bodies dominated by populations of large-bodied fish may
support relatively high avian species richness as well,
provided that a considerable emergent vegetation cover is
preserved. Management of habitats with size-structured fish
communities can be specified to target selected bird species,
e.g., by omitting piscivorous species at fisheries, to accom-
modate both wildlife conservation and economic interests.
Acknowledgments We are grateful to the fish farmers (M. Filipiak,
J. Orzepowski, and M. Sagan) for their help and for regular access to
the ponds. Comments from three anonymous referees greatly
improved the manuscript. This research was funded by grants from
the State Committee for Scientific Research (KBN 6 PO4F 066 20 and
3 PO4F 036 23).
References
Allen J, Nuechterlein G, Buitron D (2007) Resident nongame
waterbird use following biomanipulation of a shallow lake. J
Wildl Manage 71:11581162
Bajer PG, Sullivan G, Sorensen PW (2009) Effects of rapidly
increasing population of common carp on vegetative cover and
waterfowl in a recently restored Midwestern shallow lake.
Hydrobiologia 632:235245
Bandorf H (1970) Der Zwergtaucher (Tachybaptus rufficolis). Ziemsen,
Wittenberg Lutherstadt
Bibby CJ, Burgess ND, Hill DA, Mustoe SH (2000) Bird census
techniques, 2nd edn. Academic, London
Brenninkmeijer A, Stienen EWM, Klassen M, Kersten M (2002)
Feeding ecology of wintering terns in Guinea-Bissau. Ibis
144:602613
Cezilly F (1992) Turbidity as an ecological solution to reduce the
impact of fish-eating colonial waterbirds on fish farms. Col
Waterbirds 15:249252
Cramp S (1985) Handbook of the birds of Europe and the Middle East
and North Africa, vol 4. Oxford University Press, Oxford
Crivelli AJ (1983) The destruction of aquatic vegetation by carp.
Hydrobiologia 106:3741
Diamond J (1986) Overview: laboratory experiments, field experi-
ments, and natural experiments. In: Diamond J, Case TJ (eds)
Community ecology. Harper and Row, New York, pp 321
Driver PD, Closs GP, Koen T (2005) The effects of size and density of
carp (Cyprinus carpio L.) on water quality in an experimental
pond. Arch Hydrobiol 163:117131
Eadie JM, Keast A (1982) Do Goldeneye and perch compete for food?
Oecologia 55:225230
Elmberg J, Nummi P, Poeysae H, Sjoeberg K (1994) Relationships
between species number, lake size and resource diversity in
assemblages of breeding waterfowl. J Biogeogr 21:7584
Englund G, Johansson F, Olsson TI (1992) Asymmetric competition
between distant taxa: poeciliid fishes and water striders.
Oecologia 92:498502
Eriksson MOG (1979) Competition between freshwater fish and Gold-
eneyes Bucephala clangula (L.) for common prey. Oecologia
41:99107
Fjeldså J (1982) The adaptive significance of local variations in the
bill and jaw anatomy of North European red-necked grebes
Podiceps grisegena. Ornis Fenn 59:8498
Fjeldså J (2004) The GrebesPodicipedidae. Oxford University
Press, Oxford
Gilbert G, Tyler G, Smith KW (2003) Nestling diet and fish
preference of bitterns Botaurus stellaris in Britain. Ardea
91:3544
Giles N (1994) Tufted duck (Aythya fuligula) habitat use and brood
survival increases after fish removal from gravel pit lakes.
Hydrobiologia 279(280):387392
Griffiths RA (1985) A simple funnel trap for studying newt
populations and an evaluation in smooth and palmate newts,
Triturus vulgaris and Triturus helveticus. Br J Herpetol 1:510
Grimmet RFA, Jones TA (1989) Important bird areas in Europe. ICBP
Technical Publ. no. 9, Cambridge
Haas K, Köhler U, Diehl S, Köhler P, Dietrich S, Holler S, Jensch A,
Niedermaier M, Vilsmeier J (2007) Influence of fish on habitat
choice of water birds: a whole-system experiment. Ecology
88:29152925
Hargeby A, Andersson G, Blindow I, Johansson S (1994) Trophic
web structure in a shallow eutrophic lake during a dominance
shift from phytoplankton to submerged macrophytes. Hydro-
biologia 279(280):8390
Hill D, Wright R, Street M (1987) Survival of mallard ducklings Anas
platyrhynchos and competition with fish for invertebrates on a
flooded gravel quarry in England. Ibis 129:159167
Holmgren K, Appelberg M (2000) Size structure of benthic freshwater
fish communities in relation to environmental gradients. J Fish
Biol 57:13121330
Holopainen IJ, Hyvarinen H (1985) Ecology and physiology of
crucian carp [Carassius carassius (L.)] in small Finnish ponds
with anoxic conditions in winter. Verh Int Verein Limnol
22:25662570
Hurlbert SH, Loayza W, Moreno T (1986) Fishflamingoplankton
interactions in the Peruvian Andes. Limnol Oceanogr 3:457468
Jenkins RKB, Ormerod SJ (2002) Habitat preferences of breeding
water rail Rallus aquaticus. Bird Study 49:210
Kloskowski J (2004) Food provisioning in red-necked grebes
(Podiceps grisegena) at common carp (Cyprinus carpio) ponds.
Hydrobiologia 525:131138
Kloskowski J (2009) Size-structured effects of common carp on
reproduction of pond-breeding amphibians. Hydrobiologia
635:205213
Koskimies P, Väisänen RA (1991) Monitoring bird populations. A
manual of methods applied in Finland. Zool. Mus., Finnish Mus.
Nat. Hist., Univ. Helsinki, Helsinki
Lammens EHRR (1999) The central role of fish in lake restoration and
management. Hydrobiologia 396:191198
Lammens EHRR, Hoogenboezem W (1991) Diets and feeding
behaviour. In: Winfield IJ, Nelson JS (eds) Cyprinid fishes:
systematics, biology and exploitation. Chapman and Hall,
London, pp 353376
Levins R (1979) Asymmetric competition among distant taxa. Am
Zool 19:10971104
Naturwissenschaften (2010) 97:673682 681
Lind OT (1985) Handbook of common methods in limnology.
Kendall/Hunt, Dubuque
Mallory ML, Blancher PJ, Weatherhead PJ, McNicol DK (1994)
Presence or absence of fish as a cue to macroinvertebrate
abundance in boreal wetlands. Hydrobiologia 279280:345351
McParland CE, Paszkowski CA (2006) Effects of small-bodied fish on
invertebrate prey and foraging patterns of waterbirds in Aspen
Parkland wetlands. Hydrobiologia 567:4355
Meijer ML, Lammens EH, Raat AJP, Grimm MP, Hosper SH (1990)
Impact of cyprinids on zooplankton and algae in ten drainable
ponds. Hydrobiologia 191:275284
Moran MD (2003) Arguments for rejecting the sequential Bonferroni
in ecological studies. Oikos 100:403405
Moser ME (1986) Prey profitability for adult grey herons Ardea
cinerea and the constraints on prey size when feeding young
nestlings. Ibis 128:392405
Mraz D, Cooper EL (1957) Natural reproduction and survival of carp
in small ponds. J Wildl Manage 21:6669
Murkin HR, Abbott PG, Kadlec JA (1983) A comparison of activity
traps and sweep nets for sampling nektonic invertebrates in
wetlands. Freshw Invertebr Biol 2:99106
Nummi P, Pöysä H, Elmberg J, Sjöberg K (1994) Habitat distribution
of the mallard in relation to vegetation structure, food, and
population density. Hydrobiologia 279280:247252
Panek FM (1987) Biology and ecology of carp. In: Cooper EL (ed)
Carp in North America. American Fisheries Society, Bethesda,
pp 115
Paszkowski CA, Tonn WM (2000) Community concordance between
the fish and aquatic birds of lakes in northern Alberta, Canada:
the relative importance of environmental and biotic factors.
Freshw Biol 43:421437
Penttinen O-P, Holopainen IJ (1992) Seasonal feeding activity and
ontogenetic dietary shifts in crucian carp, Carassius carassius.
Env Biol Fishes 33:215221
Persson L (1988) Asymmetries in competitive and predatory inter-
actions in fish populations. In: Ebenman B, Persson L (eds) Size-
structured populations: ecology and evolution. Springer, Berlin,
pp 203218
Polak M (2007) Food of nestling great bitterns Botaurus stellaris at
fishpond complexes in eastern Poland. Bird Study 54:280283
Ranoszek E (1983) Test for methods of number estimation of breeding
water birds. Not Ornitol 24:177201 (In Polish)
Richardson MJ, Whoriskey FG (1992) Factors influencing the
production of turbidity by goldfish. Can J Zool 70:15851589
Safina C, Burger J (1985) Common tern foragingseasonal trends in
prey fish densities and competition with bluefish. Ecology
66:14571463
Sargeant AB, Raveling DG (1992) Mortality during the breeding
season. In: Batt DDJ (ed) Ecology and management of breeding
waterfowl. Univ. Minnesota Press, Minneapolis, pp 396422
Suter W (1991) Der Einfluß fischfressender Vogelarten auf
Süßwasserfischbeständeeine Übersicht. J Ornithol 132:2945
ter Braak CJF, Šmilauer P (2002) CANOCO reference manual and
CanoDraw for Windows User_s guide: software for Canonical
Community Ordination (version 4.5). Microcomputer Power,
Ithaca
Tonn WM, Magnuson JJ (1982) Patterns in the species composition
and richness of fish assemblages in northern Wisconsin Lakes.
Ecology 63:11491166
van Eerden MR, Piersma T, Lindeboom R (1993) Competitive food
exploitation of Smelt Osmerus eperlanus by great crested grebes
Podiceps cristatus and perch Perca fluviatilis at Lake Ijsselmeer,
The Netherlands. Oecologia 93:463474
Weller MW (1999) Wetland birds: habitat resources and conservation
implications. Cambridge University Press, Cambridge
Zambrano L, Scheffer M, Martínez-Ramos M (2001) Catastrophic
response of lakes to benthivorous fish introduction. Oikos
94:344350
682 Naturwissenschaften (2010) 97:673682
... In Mallard, for instance, plant seeds are increasing in percentage with duckling age, while invertebrates are on decrease (Drilling et al. 2020). The studied species feed mostly on or amongst water vegetation (Billerman et al. 2020 some studies Mallard was recorded among reeds in much greater percentage (Ulenaers & Dhondt 1991, Hattori & Mae 2001, Kloskowski et al. 2010. Apart from food and hunting, water birds use water vegetation also as a safe nesting or resting area (Kloskowski et al. 2010), as also noted at Rački ribniki (Martinc 2015). ...
... The studied species feed mostly on or amongst water vegetation (Billerman et al. 2020 some studies Mallard was recorded among reeds in much greater percentage (Ulenaers & Dhondt 1991, Hattori & Mae 2001, Kloskowski et al. 2010. Apart from food and hunting, water birds use water vegetation also as a safe nesting or resting area (Kloskowski et al. 2010), as also noted at Rački ribniki (Martinc 2015). ...
Article
Full-text available
The difference in habitat use by the observed waterbird species at Rački ribniki (Rače Ponds, NE Slovenia) was studied between June and August 2011. It was assessed that different waterbird species, even closely related species like Aythya ducks, use wetlands differently, with Tufted Ducks A. fuligula observed more on Open water and Ferruginous Ducks A. nyroca more often amongst Floating vegetation. The latter was used more often probably due to the abundance of food in the habitat. Highest species richness was recorded on Floating vegetation as well. This was reflected in species richness of individual ponds, where ponds with more floating vegetation had higher species richness. Although Coots Fulica atra were expected to utilize Floating vegetation more often due to their feeding preferences, they were observed more often on Open water probably feeding on fish fodder available there. The difference in habitat use by the families and nonbreeding individuals of the same species was noted, too, mostly by observing families in habitats that provide more cover from predators (Reeds), or more invertebrate food (Floating vegetation) for the young that often feed on different food than adults. Furthermore, it was suggested that overall management of wetlands should consider providing more suitable wetlands with larger aquatic vegetation cover.
... Currently, some marsh bird species exhibiting greater plasticity may be living in anthropogenic habitats (Tscharntke 1992;Ledwoń et al. 2014;Pérez-Garcia et al. 2014). Artificial fishponds, post-mining lakes or gravel pits are assumed to be suitable alternative breeding habitats for many waterbirds, including piscivorous species such as herons (Santoul et al. 2009;Kloskowski et al. 2010;Sebastián-González et al. 2010;Trnka 2020). Therefore, studying the habitat choice of waterbird species in these altered and man-made habitats may improve their conservation prospects (Amano et al. 2018). ...
... In natural and semi-natural habitats like fishponds, nest predation is a major cause of brood losses among marshland birds so the presence of water below and around the nest is a significance hindrance to predators (Polak 2007;Polak et al. 2008;Jedlikowski et al. 2016). Furthermore, stable hydrological conditions throughout the breeding season ensure access to food (Kloskowski et al. 2010). In our study, too, the water level was a significant environmental factor affecting the distribution of Little Bitterns. ...
... Finally, invertebrate-feeding leech densities could have been underestimated in highfish ponds, as they may be less active in the presence of potential predators (Davies & Kasserra 1989). Similarly, traps in low-fish ponds captured large numbers of invertebrates and tadpoles (Kloskowski et al. 2010;Nieoczym & Kloskowski 2015), which potentially could attract predatory and liquidosomatophagous leeches (cf. Verdonschot 2010). ...
... Although vertebrate predators are believed to constitute the principal threat to leeches, predatory arthropods can exert a significant trophic effect as well (Young & Spelling 1986;Spelling & Young 1987;Cywinska & Davies 1989;Cobbaert et al. 2010). In contrast to high-fish ponds, low-fish ponds abound in amphibians, waterfowl, and predatory insects (Kloskowski et al. 2010;Nieoczym & Kloskowski 2015). Consequently, leeches, provided that they are able to persist in the presence of fish, may indirectly benefit from the adverse effects of fish on populations of large predatory insects as well as on amphibians and invertebrate-feeding waterbirds. ...
... Semiaquatic vertebrate predators can swim or dive into the water to capture their preys, while many terrestrial predators feed on invertebrates along the shores when they emerge from the water. Evidence that terrestrial and semiaquatic vertebrates can compete with fish for aquatic invertebrates and emerging insects has been found in controlled experimental conditions (Cabrera-Guzmán et al., 2017) as well as in natural aquatic ecosystems including rivers (LeBourdais et al., 2009), wetlands (Hornung and Foote, 2006), intertidal zones (Furness et al., 1986), the open ocean (Toge et al., 2011), and lentic systems as diverse as saline mountain lakes (Hurlbert et al., 1986), ponds (Haas et al., 2007;Kloskowski et al., 2010), oligotrophic lakes (Eriksson, 1979;Epanchin et al., 2010;Hancock et al., 2023;Joseph et al., 2011;Nummi et al., 2012), and large eutrophic lakes (Winfield and Winfield, 1994). ...
Article
Full-text available
Widespread fish introductions into originally fishless mountain lakes have had severe consequences for native biota, including aquatic macroinvertebrates, which provide important food subsidies for terrestrial and semiaquatic insectivores like shrews (Fam. Soricidae). Since both fish and shrews rely on aquatic macroinvertebrates as food, whether in their larval or imaginal stage, we investigated if fish presence had adverse effects on shrews. Baited tubes were deployed to monitor the presence/absence of shrews by collecting their scats in lakes with and without fish in the western Italian Alps. Only two species, the Valais shrew (Sorex antinorii) and the Eurasian water shrew (Neomys fodiens), were found inhabiting the lakes' edges, where they fed on aquatic insect subsidies. The results indicate a significant pattern of exclusion between shrews and introduced fish. This negative association was especially evident in the presence of large-bodied fish (i.e., salmonids), but also of small fish (i.e., cyprinids). Consistently, compared to naturally fishless lakes, those with fish exhibit a lower availability of aquatic prey, representing a significant portion of the diet of both shrew species. Overall, our findings suggest that the impact on shrews may be mediated by a complex interplay of competition and predation between fish and shrews. Fish impacts may extend beyond the lakes to insectivorous mammals in surrounding areas. We recommend that the potential benefits to species and habitats reliant on aquatic subsidies be considered and integrated into conservation and restoration plans, and that these findings be communicated to the public to foster greater support for restoration efforts.
... In terms of species richness and migratory abundance, the Chametla wetland is one of the most important sites for birds along the Baja California Peninsula, providing various resources for feeding, resting and breeding individuals of both resident and migratory bird species (Becerril and Carmona 1997;Fernández et al. 1998;Brabata and Carmona 1999). Waterbirds are frequently related to the abundance and variety of fish and invertebrates (Kloskowski et al. 2010;Pérez-Vargas et al. 2016), which, in the study area, are the lowest in winter, following high predation pressure from autumn migrating shorebirds (Leija-Tristán et al. 1990;González-Acosta et al. 2005). ...
Article
The Chametla wetland is used by shorebirds as a stopover site during their autumn migration and it is also an important breeding area for several species of waterbirds. The objective of this work was to compare the bird assemblages in Chametla wetland during three sampling periods: 1) 1991-1992; 2) 1997-1998 which was subjected to El Nino Southern Oscillation (ENSO) climate conditions and 3) 2005-2006. Bird communities were characterized in terms of species composition and diversity, using similarity analysis. Bird assemblage composition differed across years and seasons. Seasonal variations in composition and diversity were related to the presence/absence of phenological-characterized species (migratory vs. wintering species). The highest species richness was recorded under the ENSO period (1997-1998). We observed a sharp decrease in shorebird numbers, with evident stress at the assemblage level throughout the entire study period. There seems to be a transition of the bird assemblages from shorebird dominance to a dominance by long-legged wading birds and waterfowl species, which could be related to water level variation and changes in the quality/availability of food in the intertidal zone. The joint pressures of regional climate variation combined with local anthropogenic perturbations may lead to changes in bird assemblage in the Chametla wetland.
... In terms of species richness and migratory abundance, the Chametla wetland is one of the most important sites for birds along the Baja California Peninsula, providing various resources for feeding, resting and breeding individuals of both resident and migratory bird species (Becerril and Carmona 1997;Fernández et al. 1998;Brabata and Carmona 1999). Waterbirds are frequently related to the abundance and variety of fish and invertebrates (Kloskowski et al. 2010;Pérez-Vargas et al. 2016), which, in the study area, are the lowest in winter, following high predation pressure from autumn migrating shorebirds (Leija-Tristán et al. 1990;González-Acosta et al. 2005). ...
... Several environmental factors influence waterbird use of aquaculture ponds, including area, water depth, bank vegetation, and the species and size of cultured aquatic organisms (Froneman et al. 2001, Kloskowski et al. 2010, Sebastián-González and Green 2014, Feaga et al. 2015, Burr et al. 2020, Wang et al. 2020. Water depth, in particular, plays a key role in the waterbird utilization of aquaculture ponds. ...
... W sezonach, gdy staw był zarybiony tylko kroczkiem występowało tam regularnie 50-200 grążyc (dane własne). Kolejny przykład, spotykany na każdym większym kompleksie stawów, to przemieszczenia grążyc na stawy narybkowe napełniane od drugiej połowy maja co jest związane z ob tą bazą pokarmową (Kloskowski et al. 2010, Nieoczym 2012. W warunkach stawów w Biechowie, kaczki z głównego kompleksu przelatują na kilka stawów w promieniu do 4 km i czyni to średnio nawet 30-50% grążyc (dane własne). ...
Article
Full-text available
In the present paper, I discussed methodological and interpretative errors in the Wetland Bird Survey (MPM) and Ferruginous Duck Census (MPO) – two programs carried out as a part of the Monitoring of Birds in Poland. The sample data collected in the MPM are not representative of breeding populations of ducks and do not detect similar population proportions in subsequent years. The comparison of the MPM results (8 transects x 1 km) and the large-scale survey on fish ponds (6936 ha) showed a drastic discrepancy in the determined abundance trends. The shortcomings of the MPM are counts of ducks on transects instead of the extensive areas, too long count periods, which should be shortened to several days, counts that do not account for sexes, and flawed data interpretation, in which the seasonal abundance of ducks on sample plots is determined by the illegitimate mixing of birds from different phenological periods. The problems in the MPO are the wrong count dates and errors in data interpretation – the same individuals are summed up several times, there is a significant share of birds for which sex is not determined, and the criteria for qualifying “breeding pairs” are vague. The MPM constantly provides results contradictory to the facts, and the MPO provides scientifically inadequate data. It is recommended to stop the monitoring of ducks within the MPM and to remove from the discourse all trends and estimates based on the results of this project. In the MPO, the estimates for previous years should be verified, and only the number of females recorded in mid-May should be account for as the assessment of the size of the population. It is also necessary to limit the date of the count in May and postpone to the 2nd decade of July or even completely abandon the second control aiming to determine the breeding success. Keywords: ducks, Anatinae, diving ducks, Aythyini, dabbling ducks, Anatini, monitoring, sample representativeness, abundance trends, Wetland Bird Survey, Ferruginous Duck Census, Monitoring of Birds in Poland.
... However, fish culture practices, such as specific fish stocking strategies, determine the abundance and diversity of prey for waterbirds (Horváth et al. 1992;Haas et al. 2007;Kloskowski 2011Kloskowski , 2012. The principal aim of aquaculture is the rapid production of large marketable fish, but this constrains suitable foraging and breeding habitats of many waterbirds (Kloskowski et al. 2010;Kloskowski 2012). Fish, though typically more profitable prey than invertebrates or amphibian larvae (Jackson 2003), can interact with birds as competitors capable of strong indirect effects (Kloskowski 2011;Nummi et al. 2016;Maceda-Veiga et al. 2017). ...
Article
Full-text available
Knowledge of the relationships between food habits and habitat is crucial for the assessment of habitat quality for birds. The present study investigated the diet and reproductive success of Little Bitterns Ixobrychus minutus nesting on cyprinid fish ponds, an important breeding habitat of this species in central and eastern Europe. Being subject to different management practices, fish ponds provide food resources of uneven availability for this small heron. Prey items regurgitated by nestlings were examined, and breeding success was estimated on monoculture ponds stocked either with small fish (of a size suitable for feeding nestlings) or large fish (unavailable to Little Bitterns and adversely affecting their non-fish prey), on abandoned ponds dominated by small fish but with large fish also present, and on angling ponds dominated by large sport fish but harbouring significant numbers of small fish as well. A total of 1356 prey items from 78 broods were identified. Although Little Bitterns exhibited dietary flexibility in response to the contrasting availability of prey on their nesting ponds, the bulk of the nestlings’ diet consisted of fish. The size of fish brought to the nest increased significantly with brood age, showing that parents adjusted the prey size to the gape constraints of their young. The chick production determined for 73 broods did not differ with respect to pond management, but the dietary composition indicated that to compensate for food shortages, birds nesting on ponds containing mainly large fish made foraging flights to food-richer ponds. The abundance of small-sized fish prey may be a factor limiting the breeding success of small- and medium-sized predatory waterbirds and should be taken into consideration in management strategies of habitats dominated by fish.
... Several environmental factors influence waterbird use of aquaculture ponds, including area, water depth, bank vegetation, and the species and size of cultured aquatic organisms (Froneman et al. 2001, Kloskowski et al. 2010, Sebastián-González and Green 2014, Feaga et al. 2015, Burr et al. 2020, Wang et al. 2020. Water depth, in particular, plays a key role in the waterbird utilization of aquaculture ponds. ...
Preprint
Full-text available
The loss of coastal wetlands represents a grave threat to waterbirds, prompting the use of artificial wetlands, such as aquaculture ponds, as a means of conservation. Aquaculture ponds are common in coastal areas and provide production value and ecological function as waterbird habitats. However, certain piscivorous birds may cause economic losses to the aquaculture industry. Different types of ponds provide habitat for various bird assemblages, and waterbirds exhibit nocturnal feeding behavior and utilize habitats distinct from those used during the day. Most waterbird surveys were conducted during the daytime, limiting our understanding of their nocturnal habitat utilization. This study conducted diurnal and nocturnal surveys on shorebirds, waterfowl, and Black-crowned Night Heron ( Nycticorax nycticorax ) ten times in three aquaculture ponds situated in the Cigu District of Tainan, namely fish/shrimp, hard clam, and abandoned ponds between October 2021 and November 2022. The results showed no significant difference in shorebird density between day and night. However, shorebird density in fish/shrimp ponds was significantly higher than in abandoned ponds. Conversely, waterfowl density exhibits a significant increase in abandoned ponds compared to the other two pond types, irrespective of diurnal or nocturnal conditions. Furthermore, waterfowl density in abandoned ponds was significantly higher during daylight compared to the nocturnal period. In the daytime, the density of night herons was significantly higher in abandoned ponds than in the other two ponds. Nevertheless, during nighttime, fish/shrimp ponds exhibit the highest density of night herons, significantly surpassing that found in hard clam ponds. Notably, water coverage also influences the density of both shorebirds and waterfowl. The foraging frequency of waterfowl and night herons was greater during nocturnal hours, while shorebirds did not exhibit significant variations between day and night. Consequently, this study underscores the significance of considering both diurnal and nocturnal habitats in formulating strategies for waterbird conservation.
Article
Full-text available
Capsule Surveys using broadcast vocalizations during the breeding season found that Water Rail were significantly more abundant at sites that contained the most wet reed Phragmites sp. Aim To field test a survey method for estimating the abundance of breeding Water Rail and to provide an assessment of coarse-scale habitat selection. Methods Water Rails were surveyed in 1996-97 at 77 wetland sites across Wales using broadcast vocalizations from a handheld cassette player. Volunteers were recruited to allow maximum geographical coverage during the month-long survey period, generally making three early morning visits to each site. Basic habitat characteristics were recorded for all sites and more detailed information, including freshwater invertebrate samples, were taken from a subset of 22 sites. Results A minimum of 43 to 49 breeding pairs of Water Rail were counted. Numbers of individuals differed significantly between the two survey years, but estimates of the number of pairs were consistent. Water Rail occurrence at a site was significantly related to the presence of wet reed Phragmites sp. Dry sites with low vegetation cover were the least occupied. Water Rail abundance was positively correlated with the abundance of Odonata, Plecoptera and Diptera larvae, but lack of data on actual dietary composition prohibits concluding a causal relationship. Conclusion We hypothesize that increased Water Rail abundance associated with expanses of wet reed reflects a combination of nest safety, reduced risk of predation, and increased food availability. Current reed-bed management to maintain wetland conditions, often standard procedures for such systems, are probably beneficial to Water Rail. This work demonstrates that useful information on ecological preferences for otherwise secretive birds can be obtained from vocalization surveys.
Book
Wetland birds provide us with some of nature's most wonderful sights, from vast flocks wheeling overhead to newly-hatched chicks drying in the sun. Apart from their beauty, recreational and economic importance, they are excellent indicators of water quality and measures of biodiversity. But how do they use wetland habitats, and how can we best conserve and maintain them for the future? Here, Milton Weller describes the ecology of wetland birds by identifying patterns of habitat use and typical bird communities that result from the use of resources such as food, cover and breeding sites. He integrates basic and practical information on bird/habitat relationships for researchers, landowners, managers and keen birders alike. As wetlands continue to decline, this book will help us to understand the potential and limits of wetlands as bird habitats now and in the future.
Article
The first assessment of both nestling diet composition and selection of fish prey by Bitterns Botaurus stellaris in Britain. We provide quantitative information on the diet of nestling Bitterns, examine the factors influencing diet composition and determine whether adult females are choosing particular species and size of prey. Sixty regurgitate samples from 44 broods were examined during visits to Bittern nests made at nine sites in England from 1996 to 2001. Compositional analysis was used to assess influence of age, season and year effects on diet. The fish component of the diet was compared with species found to be generally available within each site from electro fishing data. Eel Anguilla anguilla and Rudd Scardinius erythrophthalmus made up the greatest proportion of biomass of the diet and this proportion did not significantly change with the age of the chicks. The amount of Eel in the diet changed during the season and the amount of Rudd between years. From those fish species available, female Bitterns preferred to feed chicks on Nine-spined Sticklebacks Pungitius pungitius, Eels (0-40g), Three-spined Sticklebacks Gasterosteus aculeatus and Rudd (0-20g). It is likely that female Bitterns feeding young in Britain have a limited prey choice. To optimise food availability we need better understanding of the seasonal habitat requirements of key fish species within reedbed-dominated sites.