Energetic implications of floodplain wetland restoration strategies for waterfowl

Modifications of the Illinois River and associated tributaries have resulted in altered hydrologic cycles and persistent river‐floodplain connections during the growing season that frequently impede the establishment of hydrophytic vegetation and have reduced value for migratory waterfowl and other waterbirds. To help guide floodplain restoration, we compared energetic carrying capacity for waterfowl in two wetland complexes along the Illinois River under different management regimes during 2012–2015. The south pool of Chautauqua National Wildlife Refuge (CNWR) was seasonally flooded due to a partial river connection and managed for moist‐soil vegetation. Emiquon Preserve was hydrologically isolated from the Illinois River by a high‐elevation levee and managed as a semipermanently flooded emergent marsh. Semipermanent emergent marsh management at Emiquon Preserve produced 5,495 energetic use‐days (EUD)/ha for waterfowl and other waterbirds across wetland cover types and years, and seasonal moist‐soil management at CNWR produced 6,199 EUD/ha in one of 4 years. At Emiquon Preserve, the aquatic bed cover type produced 9,660 EUD/ha, followed by 5,261 EUD/ha in moist‐soil, 1,398 EUD/ha in persistent emergent, 1,185 EUD/ha in hemi‐marsh, and 12 EUD/ha in open water cover types. At CNWR, the annual grass and sedge cover type produced 7,031 EUD/ha, followed by 5,618 EUD/ha in annual broadleaf and 1,305 EUD/ha in perennial grass cover types. Restoration of floodplain wetlands in isolation from frequent flood pulses during the growing season can produce hemi‐marsh and aquatic bed vegetation communities that provide high‐quality habitat for waterfowl and which have been mostly eliminated from large river systems in the Midwest, U.S.A.     

Wetland Selection by Mallard Broods in Canada's Prairie-Parklands

ABSTRACT Although brood survival has a pronounced effect on population growth in mallards (Anas platyrhynchos), knowledge of brood ecology is more limited than for other vital rates. During 1993–1997 we collected wetland selection data from 210 radiomarked mallard broods on 15 study areas located throughout the Canadian Prairie-Parklands. We used information-theoretic approaches to select the best-approximating model of habitat selection in relation to wetland characteristics. Wetland permanence, cover type, width of flooded emergent vegetation, and interactions between these variables and date, moisture level, and dominant species of emergent vegetation were all important predictors of wetland selection. Mallard broods selected deeper wetlands, especially later in the brood-rearing season. Mallard broods also selected wetlands with large central expanses of open water and wide peripheral zones of flooded emergent cover. These habitat characteristics can most easily be met in landscapes that already contain an abundance and diversity of natural wetland habitats. Where such wetlands are unavailable, restoration or management of deeper wetlands may be necessary to meet the habitat requirements of mallard ducklings.     

Lesser Scaup Breeding Probability and Female Survival on the Yukon Flats,Alaska

ABSTRACT Information on the ecology of waterfowl breeding in the boreal forest is lacking, despite the boreal region's importance to continental waterfowl populations and to duck species that are currently declining, such as lesser scaup (Aythya affinis). We estimated breeding probability and breeding season survival of female lesser scaup on the Yukon Flats National Wildlife Refuge, Alaska, USA, in 2005 and 2006. We captured and marked 93 lesser scaup with radiotransmitters during prelaying and nesting periods. Although all marked lesser scaup females were paired throughout prelaying and incubation periods, we estimated breeding probability over both years as 0.12 (SE = 0.05, n = 67) using telemetry. Proportion of lesser scaup females undergoing rapid follicle growth at capture in 2006 was 0.46 (SE = 0.11, n = 37), based on concentration of yolk precursors in blood plasma. By combining methods based on telemetry, yolk precursors, and postovulatory follicles, we estimated maximum breeding probability as 0.68 (SE = 0.08, n = 37) in 2006. Notably, breeding probability was positively related to female body mass. Survival of female lesser scaup during the nesting and brood-rearing periods was 0.92 (SE = 0.05) in 2005 and 0.86 (SE = 0.08) in 2006. Our results suggest that breeding probability is lower than expected for lesser scaup. In addition, the implicit assumption of continental duck-monitoring programs that all paired females attempt to breed should be reevaluated. Recruitment estimates based on annual breeding-pair surveys may overestimate productivity of scaup pairs in the boreal forest.     

Seed bank potential of moist-soil managed wetlands in east-central Texas

Proper management techniques on moist-soil wetlands provide methods for enhancement of established wetlands, restoration of former wetlands, and creation of new wetland habitat. These techniques also create suitable wetland habitat for non-breeding waterfowl and other wetland dependent species during winter. To understand moist-soil managed wetland vegetative patterns, aspects such as plant species distribution, reproductive strategy, seed bank composition and viability should be thoroughly characterized. We investigated soil seed bank potential of moist-soil managed wetlands on Richland Creek Wildlife Management Area, Texas to determine which treatment (i.e., drawdown or flooded) produced the most desirable moist-soil plants. A total of 27 species germinated, producing 3,731 and 3,031 seedlings in drawdown and flooded treatments, respectively. There were also differences in stem densities between treatments of desirable and non-desirable species. Drawdown treatments had more seedlings germinate than flooded treatments, validating the notion that drawdown treatments provide favorable conditions for seed germination. Drawdown and flooding techniques, when properly timed, will allow managers to drive and directly influence managed wetland plant communities based on seed bank composition and response to presence or absence of water during the germination period.     

Habitat edges affect patterns of artificial nest predation along a wetland-meadow boundary

Wetland habitats are among the most endangered ecosystems in the world. However, little is known about factors affecting the nesting success of birds in pristine grass-dominated wetlands. During three breeding periods we conducted an experiment with artificial ground nests to test two basic mechanisms (the matrix and ecotonal effects) that may result in edge effects on nest predation in grass-dominated wetland habitats. Whereas the matrix effect model supposes that predator penetrate from habitat of higher predator density to habitat of lower predator density, thus causing an edge effect in the latter, according to the ecotonal effect model predators preferentially use edge habitats over habitat interiors. In addition, we tested the edge effect in a wetland habitat using artificial shrub nests that simulated the real nests of small open-cup nesting passerines. In our study area, the lowest predation rates on ground nests were found in wetland interiors and were substantially higher along the edges of both wetland and meadow habitat. However, predation was not significantly different between meadow and wetland interiors, indicating that both mechanisms can be responsible for the edge effect in wetland edges. An increased predation rate along wetland edges was also observed for shrub nests, and resembled the predation pattern of real shrub nests in the same study area. Though we are not able to distinguish between the two mechanisms of the edge effect found, our results demonstrate that species nesting in wetland edges bordering arable land may be exposed to higher predation. Therefore, an increase in the size of wetland patches that would lead to a reduced proportion of edge areas might be a suitable management practice to protect wetland bird species in cultural European landscapes.     

Migration stopover ecology of Cinnamon Teal in western North America

Identifying migration routes and fall stopover sites of Cinnamon Teal (Spatula cyanoptera septentrionalium) can provide a spatial guide to management and conservation efforts, and address vulnerabilities in wetland networks that support migratory waterbirds. Using high spatiotemporal resolution GPS‐GSM transmitters, we analyzed 61 fall migration tracks across western North America during our three‐year study (2017–2019). We marked Cinnamon Teal primarily during spring/summer in important breeding and molting regions across seven states (California, Oregon, Washington, Idaho, Utah, Colorado, and Nevada). We assessed fall migration routes and timing, detected 186 fall stopover sites, and identified specific North American ecoregions where sites were located. We classified underlying land cover for each stopover site and measured habitat selection for 12 land cover types within each ecoregion. Cinnamon Teal selected a variety of flooded habitats including natural, riparian, tidal, and managed wetlands; wet agriculture (including irrigation ditches, flooded fields, and stock ponds); wastewater sites; and golf and urban ponds. Wet agriculture was the most used habitat type (29.8% of stopover locations), and over 72% of stopover locations were on private land. Relatively scarce habitats such as wastewater ponds, tidal marsh, and golf and urban ponds were highly selected in specific ecoregions. In contrast, dry non‐habitat across all ecoregions, and dry agriculture in the Cold Deserts and Mediterranean California ecoregions, was consistently avoided. Resources used by Cinnamon Teal often reflected wetland availability across the west and emphasize their adaptability to dynamic resource conditions in arid landscapes. Our results provide much needed information on spatial and temporal resource use by Cinnamon Teal during migration and indicate important wetland habitats for migrating waterfowl in the western United States.     

Livestock grazing in intermountain depressional wetlands: effects on breeding waterfowl

Livestock grazing is a prevalent land use in western North American intermountain wetlands, and physical and biotic changes related to grazing-related disturbance can potentially limit wetland habitat value for waterfowl. We evaluated breeding waterfowl use in 34 wetlands in relation to water retention, amount of wetlands on the landscape, and livestock grazing intensity. The study was conducted over 2 years in the southern intermountain region of British Columbia, Canada. For a subset of 17 wetlands, we measured aquatic invertebrate abundance over 1 year. Waterfowl breeding pairs and broods were classified into three functional groups: dabbling ducks, and two types of diving ducks, overwater and cavity nesters. We evaluated candidate models with variables considered singly and in combination using the Akaike Information Criterion. When selected, bare ground (an indicator of grazing intensity) and wetland density were negatively associated with breeding use while wetland fullness and invertebrate density were positively associated. Each factor was a significant predictor in at least one of the models, but unexpectedly, grazing intensity was the most consistent predictor of waterfowl wetland use (e.g., it was present in more ‘best models’ than wetland fullness). Grazing was associated with declines in the number of waterfowl pairs and broods, likely mediated through effects on wetland vegetation and aquatic macroinvertebrates. Models with site- and landscape-scale variables generally performed better than simpler models. Waterfowl breeding use of wetlands can be improved by reduced livestock grazing intensity adjacent to wetlands and by grazing later in the season. Wetland water retention is also an important constraint on waterfowl use of wetlands and may become more limiting with a shifting climate.     

Habitat quality and drought effects on breeding mallard and other waterfowl populations in California,USA

As many as 500,000 waterfowl reside in California, USA, during summer, but little is known about the availability or quality of their habitats. Wetland size and distribution serve as proximate cues for habitat selection by breeding waterfowl in other parts of North America such as the Prairie Pothole Region. In heavily modified landscapes such as California's Central Valley, disturbance from factors like crop cultivation and urban development may limit access, affect survival, and decrease reproductive success. Water limitations due to recurring seasonal droughts pose another potential threat to breeding waterfowl. Spatial and temporal disparities in environmental resources may provide clearer indications of ultimate habitat selection. We addressed waterfowl habitat selection in 9 regions surveyed annually by California's Department of Fish and Wildlife to determine relative importance of drought severity, wetland area, and habitat quality on mallard (Anas platyrhynchos) and other waterfowl population dynamics from 2007–2019. High-quality habitat supports long-term population persistence of waterfowl. This study period included an extended drought (2012–2015) and flooding (2016–2017). Statewide, habitat quality was the best predictor of mallard and other waterfowl population fluctuations. The model that included intermediate habitat quality, which accounted for influence of adjacent land-use, outperformed models that included wetland area alone. At the regional level, drought severity out-ranked other variables in most regions, suggesting management at regional scales must account for climate. Drought accounted for bird declines in some regions and possible increases in others. This information could be used to identify areas for conservation priority based on projected drought frequency and severity.     

Mallard resource selection trade‐offs in a heterogeneous environment during autumn and winter

Animals select resources to maximize fitness but associated costs and benefits are spatially and temporally variable. Differences in wetland management influence resource availability for ducks and mortality risk from duck hunting. The local distribution of the Mallard (Anas platyrhynchos) is affected by this resource heterogeneity and variable risk from hunting. Regional conservation strategies primarily focus on how waterfowl distributions are affected by food resources during the nonbreeding season. To test if Mallard resource selection was related to the abundance of resources, risks, or a combination, we studied resource selection of adult female Mallards during autumn and winter. We developed a digital spatial layer for Lake St. Clair, Ontario, Canada, that classified resources important to Mallards and assigned these resources a risk level based on ownership type and presumed disturbance from hunting. We monitored 59 individuals with GPS back‐pack transmitters prior to, during, and after the hunting season and used discrete choice modeling to generate diurnal and nocturnal resource selection estimates. The model that classified available resources and presumed risk best explained Mallard resource selection strategies. Resource selection varied within and among seasons. Ducks selected for federal, state and private managed wetland complexes that provided an intermediate or relatively greater amount of refuge and foraging options than public hunting areas. Across all diel periods and seasons, there was selection for federally managed marshes and private supplemental feeding refuges that prohibited hunting. Mallard resource selection demonstrated trade‐offs related to the management of mortality risk, anthropogenic disturbances, and foraging opportunities. Understanding how waterfowl respond to heterogeneous landscapes of resources and risks can inform regional conservation strategies related to waterfowl distribution during the nonbreeding season.     

Tracking palustrine water seasonal and annual variability in agricultural wetland landscapes using Landsat from 1997 to 2005

Wetlands densely populate the ecoregion transecting the center of the Prairie Pothole Region (PPR) known as the Missouri Coteau and epicenter to the most productive waterfowl‐breeding habitat in North America. These palustrine, depressional basin waters vacillate with regional drought and deluge, so surface water fluctuations over time modulate wetland productivity, habitat, and water quality functions. Models predict formidable effects of climate change on glacial basin surface waters, yet large‐scale, long‐term observation data are lacking to compare against predicted changes. Current, optical‐based water detection models do not delineate marsh vegetation from shallow, turbid, high‐chlorophyll waters common to the region. We developed a palustrine wetland spectral model for tracking open surface waters using Landsat imagery, which we evaluated for a 2500 km² landscape that estimates seasonal and annual open water variability for thousands of individual wetlands in the Missouri Coteau ecoregion. Detection accuracy of 96% was achieved for water bodies greater than a half‐pixel in size. We identified shifts in the distribution of water permanence classes within and between years for waters emerging in spring, mid‐summer, and late summer from 1997 to 2005 and identified a maximum of 19 047 basins with open water (12% of the landscape) populating 2500 km². For the 2005 growing season, we observed only 8757 basins with open water (6% of the landscape) for the same area. Declines were greatest for water bodies detected only in spring, suggesting a loss of those wetlands functioning to recharge groundwater stores early in the season and a high sensitivity to observed reductions in snowfall. If landscape factors driving open water coverage and wetland density are similar for the entire Missouri Coteau, we estimate the number of basins containing at least a pixel of water for this region declined from 577 600 to 266 000 between 1997 and 2005.     

Temporal variation in habitat selection breaks the catch‐22 of spatially contrasting predation risk from multiple predators

Predator avoidance depends on prey being able to discern how risk varies in space and time, but this is made considerably more complicated if risk is simultaneously present from multiple predators. This is the situation for an increasing number of mammalian prey species, as large carnivores recover or are reintroduced in ecosystems on several continents. Roe deer Capreolus capreolus in southern Norway illustrate a case in which prey face two predators with contrasting patterns of predation risk. They face a catch‐22 situation: spatially avoiding the risk from one predator (lynx Lynx lynx in dense habitat) implies exposure to the other (hunters in open habitat). Using GPS‐data from 29 roe deer, we tested for daily and seasonal variation in roe deer selection for habitat with respect to the habitats’ year‐round average risk level. Generally, roe deer altered their habitat selection between night and day in a pattern consistent with being able to avoid predicted risk from the nocturnal lynx during night and predicted risk from human hunters during day. However, seasonal variation in habitat selection only partially corresponded with the predicted seasonal variation in risk. Whereas roe deer avoided areas with high risk from hunters more strongly during the hunting season than in other seasons, there was a lack of selection towards areas and time periods lowering the risk of lynx predation during winter. It seems likely that the risk of starvation and thermal stress constrain roe deer habitat selection during this energetically challenging season with cold temperatures, snow cover and limited natural forage. The habitat selection pattern of roe deer fits thus only partly with the two contrasting risk gradients they face. Adjusting risk‐avoidance behavior temporally can be an adaptive response in the case of several predators whose predation patterns differ in space and time.     

Predicted Effect of Landscape Position on Wildlife Habitat Value of Conservation Reserve Enhancement Program Wetlands in a Tile‐drained Agricultural Region

Justification for investment in restored or constructed wetland projects are often based on presumed net increases in ecosystem services. However, quantitative assessment of performance metrics is often difficult and restricted to a single objective. More comprehensive performance assessments could help inform decision‐makers about trade‐offs in services provided by alternative restoration program design attributes. The primary goal of the Iowa Conservation Reserve Enhancement Program is to establish wetlands that efficiently remove nitrates from tile‐drained agricultural landscapes. A secondary objective is provision of wildlife habitat. We used existing wildlife habitat models to compare relative net change in potential wildlife habitat value for four alternative landscape positions of wetlands within the watershed. Predicted species richness and habitat value for birds, mammals, amphibians, and reptiles generally increased as the wetland position moved lower in the watershed. However, predicted average net increase between pre‐ and post‐project value was dependent on taxonomic group. The increased average wetland area and changes in surrounding upland habitat composition among landscape positions were responsible for these differences. Net change in predicted densities of several grassland bird species at the four landscape positions was variable and species‐dependent. Predicted waterfowl breeding activity was greater for lower drainage position wetlands. Although our models are simplistic and provide only a predictive index of potential habitat value, we believe such assessment exercises can provide a tool for coarse‐level comparisons of alternative proposed project attributes and a basis for constructing informed hypotheses in auxiliary empirical field studies.     

Habitat overlap of enemies: temporal patterns and the role of spatial complexity

Environmental heterogeneity can promote coexistence of conflicting species by providing spatial or temporal refuges from strong interactions (e.g., intraguild predation, competition). However, in many systems, refuge availability and effectiveness may change through time and space because of variability in habitat use by either species. Here I consider how the intensity of intraguild predation risk varies from day to night for aquatic insects that use both vegetated and open water habitats. Large (1,265 l) and small (42 l) mesocosms were used to test the hypothesis that Buenoa would choose an open-water habitat that minimized predation by the ambush predator Notonecta during the day, but that at night Buenoa would safely use both vegetated and open water. Regardless of container size, Notonecta remained in vegetated water during the day and exploited both habitats at night, despite exhibiting greatest instantaneous predation rates in open water during the day. In contrast, Buenoa maintained an even distribution throughout the mesocosms during day and night, even though habitat-specific predation risks were fivefold lower in open waters than in vegetation during the day and habitat-specific predation risk would have been reduced threefold by fully exploiting open waters. Thus, temporal heterogeneity was both beneficial and detrimental to Buenoa; darkness of night reduced predation, but spatial refuges also disappeared. Together, these patterns suggest that while environmental heterogeneity can dampen intense biotic interactions, enemies do not select habitats solely on the basis of conflict avoidance. Instead, it appears that habitat-specific variation in other biotic (e.g., visual predators) or physical factors (e.g., UV radiation) may also mediate species interactions by influencing habitat selection.     

Habitat selection by a large herbivore at multiple spatial and temporal scales is primarily governed by food resources

Habitat selection can be considered as a hierarchical process in which animals satisfy their habitat requirements at different ecological scales. Theory predicts that spatial and temporal scales should co‐vary in most ecological processes and that the most limiting factors should drive habitat selection at coarse ecological scales, but be less influential at finer scales. Using detailed location data on roe deer Capreolus capreolus inhabiting the Bavarian Forest National Park, Germany, we investigated habitat selection at several spatial and temporal scales. We tested 1) whether time‐varying patterns were governed by factors reported as having the largest effects on fitness, 2) whether the trade‐off between forage and predation risks differed among spatial and temporal scales and 3) if spatial and temporal scales are positively associated. We analysed the variation in habitat selection within the landscape and within home ranges at monthly intervals, with respect to land‐cover type and proxys of food and cover over seasonal and diurnal temporal scales. The fine‐scale temporal variation follows a nycthemeral cycle linked to diurnal variation in human disturbance. The large‐scale variation matches seasonal plant phenology, suggesting food resources being a greater limiting factor than lynx predation risk. The trade‐off between selection for food and cover was similar on seasonal and diurnal scale. Habitat selection at the different scales may be the consequence of the temporal variation and predictability of the limiting factors as much as its association with fitness. The landscape of fear might have less importance at the studied scale of habitat selection than generally accepted because of the predator hunting strategy. Finally, seasonal variation in habitat selection was similar at the large and small spatial scales, which may arise because of the marked philopatry of roe deer. The difference is supposed to be greater for wider ranging herbivores.     

Seasonal distribution of the invasive snail, <Emphasis Type="Italic">Bithynia tentaculata,</Emphasis> within infested waterbodies in Minnesota,USA, including waterfowl migration

The introduction of the invasive faucet snail (Bithynia tentaculata) and its associated trematodes, Cyathocotyle bushiensis, Sphaeridiotrema spp., and Leyogonimus polyoon, has resulted in recurring waterfowl die-offs during spring and fall migration in the Great Lakes Region, especially of Lesser scaup (Aythya affinis) and American coots (Fulica americana). Here we evaluated faucet snail habitat use and abundance in infested waterbodies in northcentral Minnesota (USA) during spring, summer, and fall of 2011–2013. We collected snail samples, along with data on abiotic and biotic variables, at 12 snail-infested waterbodies. We used Generalized Estimating Equations to develop models that explain variability in the distribution and abundance of snails within waterbodies. Models containing water depth consistently received considerable support in waterbodies where depth varied substantially; however the specific shape of these relationships varied among waterbodies. Snails used a wide range of depths, but were more likely to be present in deep portions (~6 m) of large lakes in all seasons. We found seasonal differences in the location of rafts of migrating scaup, with use of areas closer to shore in the spring, and use of areas shallower than those used most by faucet snails. Patterns in snail distribution likely influenced the availability of snails for consumption by migrating waterfowl; differences in portions of large lakes used by migratory waterfowl as stopover sites and by faucet snails may reduce exposure of migrating waterfowl to trematodes in infested lakes. However, some spatio-temporal overlap between snails and scaup occurs and explains the continuing loss of waterfowl to trematodiasis.     

Distribution of clonal growth traits among wetland habitats

Clonality resulting from the growth of specialized organs is common among plants in wetland habitats. We hypothesize that different wetland habitats select for different attributes of clonal traits. This hypothesis is based on studies of individual species but has not been previously tested at the level of habitat. We compared the functional diversity of clonal growth traits of plants in bogs, fens, wet heathlands, floodplains, river beds, open fresh water habitats, salt marshes, and open marine habitats. Clonal traits (including number of offspring, lateral spread, persistence of connections between ramets, and shoot life span) were analysed with multivariate techniques using species frequency data and with permutation tests using presence/absence data. Based on species frequencies, clonal plants in aquatic habitats (open fresh water habitats, open marine habitats, and river beds) were characterized by the abundant production of freely dispersible propagules, annual shoots, and splitting clones. Species of daily flooded salt marshes were characterized by bi-annual connections between ramets and medium dispersability. In contrast, plants in permanently wet bogs were characterized by polycyclic shoots and low offspring production. The specificity of river beds and open freshwater habitats was also confirmed by permutation tests, which gave equal weight to rare and abundant species. However, species in all other wetland habitats were characterized by the entire range of clonal traits, suggesting weak environmental filtering of analyzed traits by habitat at the present scale.     

Sackville Waterfowl Park,Sackville, New Brunswick,Canada. Baseline characterization,towards long-term monitoring

The Sackville Waterfowl Park, contains a 19 hectare shallow freshwater wetland created by reflooding a saltwater marsh that was drained three centuries ago. Its primary purpose is to provide wetland habitat and wildlife viewing opportunities to tourists and residents. This newly created, eutrophic wetland supports high densities of waterfowl, 2.1 and 3.3 brood ha^–1 in 1991 and 1992 respectively. It is hoped that long term monitoring of the Park's waterfowl population and wetland habitat will contribute to a better understanding of factors controlling breeding waterfowl populations.     

Use of Restored Small Wetlands by Breeding Waterfowl in Prince Edward Island, Canada

Abstract Since 1990 under the Eastern Habitat Joint Venture over 100 small wetlands have been restored in Prince Edward Island, Canada. Wetlands were restored by means of dredging accumulated sediment from erosion to emulate pre‐disturbance conditions (i.e., open water and extended hydroperiod). In 1998 and 1999 we compared waterfowl pair and brood use on 22 restored and 24 reference wetlands. More pairs and broods of Ring‐necked Ducks, Gadwall, Green‐winged Teal, and American Black Ducks used restored versus reference wetlands. In restored wetlands waterfowl pair density and species richness were positively correlated with wetland/cattail area, percent cattail cover, and close proximity to freshwater rivers. In addition, a waterfowl reproductive index was positively correlated with percent cattail cover. Green‐winged Teal pair occurrence in restored wetlands was positively correlated with greater amounts of open water and water depths. American Black Duck pairs occurred on most (86%) restored wetlands. Restored small wetlands likely served as stopover points for American Black Duck broods during overland or stream movements, whereas they likely served as a final brood‐rearing destination for Green‐winged Teal broods. We suggest that wetland restoration is a good management tool for increasing populations of Green‐winged Teal and American Black Ducks in Prince Edward Island.     

SHOREBIRD HABITAT USE AND NEST-SITE SELECTION IN THE PLAYA LAKES REGION

Abstract: Wetlands in the Playa Lakes Region (PLR) provide important habitats for wintering waterfowl, cranes, and both migrant and breeding shorebirds. Playa Lakes Region wetlands experience naturally fluctuating hydroperiods but are exposed to anthropogenic stresses, which are exacerbated during summer and may influence PLR wetland occupancy and selection by breeding shorebirds. We examined wetland-scale habitat use and nest-site selection of the 4 dominant shorebirds (American avocets [Recurvirostra americana], black-necked stilts [Himantopus mexicanus], killdeer [Charadrius vociferus], snowy plovers [C. alexandrinus]) nesting in playas, saline lakes, and in both created and riparian wetlands in the PLR of Texas, USA. All 4 species nested in saline lakes. Only avocets and killdeer nested in playas, and snowy plovers nested in riparian wetlands. No nests were found in created wetlands. Wetland habitat changed (P < 0.001) during the breeding season, while water habitats generally decreased. Used (i.e., shorebirds found nesting) wetlands had more (P < 0.05) mudflats than non-used (i.e., shorebirds not found nesting) wetlands, which had more (P < 0.05) dry habitats. Used and non-used wetlands had similar (P > 0.05) amounts of water habitats. Nests were located close to vegetation on bare dry ground and dry ground with vegetation. Because water is ephemeral in PLR wetlands, shorebirds must select—in a somewhat predictive manner upon arrival—wetlands with suitable nest-site and brood-rearing habitat. Although surface water is necessary for nesting, its presence is not adequate for delineating suitable PLR wetland habitat for breeding shorebirds. Our findings that created wetlands cannot compensate for regional wetland losses in habitat or function highlights the need for conservation of natural PLR wetlands     

Predation Risk Drives Habitat‐Specific Sex Ratio in a Monomorphic Species,the Brown Hare (Lepus europaeus)

In dimorphic species, sexual habitat segregation is generally explained by the differences in nutritional needs or by a trade‐off between fulfilling food requirements and avoiding predation. However, it remains unclear whether predation risk is strong enough to drive the differences in habitat use between sexes as predicted by the predation sensitivity hypothesis. Here we test in a monomorphic species, the brown hare (Lepus europaeus), the prediction that abundance of the gender more sensitive to predation is higher in safer habitat. We used data on 1645 individually marked hares in western Poland during autumn–winter seasons of 1966/1967–1978/1979 to estimate sex‐specific annual survival rates. We analyzed the stomach contents of 134 foxes shot in 1965/1966–1994/1995 to evaluate fox predation on hares. Finally, we employed data on 26 790 hares live‐trapped in 1965/1966–1994/1995 to analyze hare sex ratio across habitats. We found that male annual survival rate was lower than that of females and that the predation risk by foxes on hares was lower in agricultural than forest habitat. Our finding, that males were more often trapped by nets in agricultural than the forest habitat, provides indirect evidence for the predation sensitivity hypothesis. We conclude that predation risk can be a driving force for habitat‐specific sex ratio in a monomorphic species such as the brown hare.