Effects of Local and Landscape Variables on Wetland Bird Habitat Use During Migration Through the Rainwater Basin

ABSTRACT Staging areas and migratory stopovers of wetland birds can function as geographic bottlenecks; common dependence among migratory wetland bird species on these sites has major implications for wetland conservation. Although 90% of playa wetlands in the Rainwater Basin (RWB) region of Nebraska, USA, have been destroyed, the area still provides essential stopover habitat for up to 10 million waterfowl each spring. Our objectives were to determine local (within wetland and immediate watershed) and landscape-scale factors influencing wetland bird abundance and species richness during spring migration at RWB playas. We surveyed 36–40 playas twice weekly in the RWB and observed approximately 1.6 million individual migratory wetland birds representing 72 species during spring migrations 2002–2004. We tested a priori hypotheses about whether local and landscape variables influenced overall species richness and abundance of geese, dabbling ducks, diving ducks, and shorebirds. Wetland area had a positive influence on goose abundance in all years, whereas percent emergent vegetation and hunting pressure had negative influences. Models predicting dabbling duck abundance differed among years; however, individual wetland area and area of semipermanent wetlands within 10 km of the study wetland consistently had a positive influence on dabbling duck abundance. Percent emergent vegetation also was a positive predictor of dabbling duck abundance in all years, indicating that wetlands with intermediate (50%) vegetation coverage have the greatest dabbling duck abundance. Shorebird abundance was positively influenced by wetland area and number of wetlands within 10 km and negatively influenced by water depth. Wetland area, water depth, and area of wetlands within 10 km were all equally important in models predicting overall species richness. Total species richness was positively influenced by wetland area and negatively influenced by water depth and area of semipermanent wetlands within 10 km. Avian species richness also was greatest in wetlands with intermediate vegetation coverage. Restoring playa hydrology should promote intermediate percent cover of emergent vegetation, which will increase use by dabbling ducks and shorebirds, and decrease snow goose (Chen caerulescens) use of these wetlands. We observed a reduction in dabbling duck abundance on wetlands open to spring snow goose hunting and recommend further investigation of the effects of this conservation order on nontarget species. Our results indicate that wildlife managers at migration stopover areas should conserve wetlands in complexes to meet the continuing and future habitat requirements of migratory birds, especially dabbling ducks, during spring migration.     

Multi-species patterns of avian cholera mortality in Nebraska's Rainwater Basin

Nebraska's Rainwater Basin (RWB) is a key spring migration area for millions of waterfowl and other avian species. Avian cholera has been endemic in the RWB since the 1970s and in some years tens of thousands of waterfowl have died from the disease. We evaluated patterns of avian cholera mortality in waterfowl species using the RWB during the last quarter of the 20th century. Mortality patterns changed between the years before (1976-1988) and coincident with (1989-1999) the dramatic increases in lesser snow goose abundance and mortality. Lesser snow geese (Chen caerulescens caerulescens) have commonly been associated with mortality events in the RWB and are known to carry virulent strains of Pasteurella multocida, the agent causing avian cholera. Lesser snow geese appeared to be the species most affected by avian cholera during 1989-1999; however, mortality in several other waterfowl species was positively correlated with lesser snow goose mortality. Coincident with increased lesser snow goose mortality, spring avian cholera outbreaks were detected earlier and ended earlier compared to 1976-1988. Dense concentrations of lesser snow geese may facilitate intraspecific disease transmission through bird-to-bird contact and wetland contamination. Rates of interspecific avian cholera transmission within the waterfowl community, however, are difficult to determine.     

Patterns of habitat and invertebrate diet overlap between tiger salamanders and ducks in prairie potholes

During the breeding season, migratory waterfowl are attracted to wetlands characterized by high macroinvertebrate availability. Many of these prairie potholes are fishless and this apparent void is filled, at least partially, by tiger salamanders. Based on gut contents from 98 tiger salamanders and published diet data from over 1500 ducks, we show that there is general overlap in diet between both larval and adult tiger salamanders and 10 duck species. Furthermore, when the ducks were split into foraging guilds and compared with tiger salamanders, prey type overlap was 1.7 times higher and prey size was 1.8 times higher with dabbling ducks than diving ducks. Field surveys show that tiger salamander density is more highly correlated with diving duck density across potholes than dabbling duck density. Tiger salamanders have higher diet overlap with dabbling ducks than diving ducks whereas tiger salamanders have higher spatial overlap with diving ducks than dabbling ducks suggesting that these consumers coarsely partition diet and habitat resources. It has been reported that tiger salamanders have specialized diets that are associated with foraging preferences for benthic habitats. This view is too narrow: in southwestern Manitoba, Canada, tiger salamanders are more general consumers with diets more like dabbling ducks that forage mostly in planktonic and littoral habitats. Our results suggest that dabbling and diving ducks are, to different extents, liable to the effects of indirect interactions, specifically competition for common prey, with tiger salamanders.     

Waterbird habitat-selection during winter and spring in reclaimed coastal wetlands in Nanhui Dongtan, Shanghai

From December 2009 to May 2010 goose and duck (Anatidae) community censuses in winter and shorebird (Charadriiforms) community censuses in spring were conducted across three types artificial wetlands (urban lake wetland, restorative wetland, abandoned wetland) along the coast of Nanhui, Shanghai. Correlation analyses were undertaken between community indices and habitat factors. The results showed there were significant differences in the density of geese and ducks among the wetlands, but no difference in the number of species. The density of geese and ducks in the restorative wetland was 3.77 times that of abandoned wetland and 6.03 times that of urban lake wetlands. The number of species and density of shorebirds in restorative wetlands was 2.88 and 5.70 times that of abandoned wetlands. We found significant differences in the number and density of shorebird species between restorative and abandoned wetlands. The number of species density of geese and ducks and the Shannon-Wiener (H') index were positively correlated with water area. The number of species and H' were negatively correlated with vegetation area. The number of species, species density and H' and evenness were negatively correlated with vegetation coverage. H' was positively correlated with mean water level. The results showed that the number and density of shorebird species were positively correlated with bare muddy areas. Aquaculture ponds and paddy fields in reclaimed area is efficient sufficient compensation mechanism to maintain more water areas for waterbirds and to control vegetation expansion and maintain shorebird habitat after coastal reclamation.     

Factors Affecting Wetland Use by Spring Migrating Ducks in the Southern Prairie Pothole Region

There is increasing recognition of the importance of wetlands in the prairie pothole region (PPR) of the northern United States for stopover habitat for spring-migrating waterfowl. The quality and quantity of stopover habitat found near breeding areas can affect speed and success of migration and subsequent breeding events. Conservation and management of wetlands in the region has traditionally focused narrowly on reproductive phases of the life cycle, and little to no research has examined how ducks use a diversity of available wetlands in the region during migration. We conducted weekly surveys on 1,061 wetlands during spring 2018 and 2019 to examine factors affecting duck use of wetlands in the intensively modified southern PPR landscape of Iowa, USA, for wetland restoration and conservation strategies. We compared wetland types, which included farmed, seasonal, and semi-permanent wetlands, and lakes. The highest duck use per unit area occurred on semi-permanent wetlands, followed by seasonal, and then farmed wetlands, and lakes. Ducks were highly clustered in our study, with 75% of all use-days occurring on only 37 wetlands comprising 41% of all wetland area surveyed. We used hurdle models to examine how local and landscape factors measured within and around wetlands influenced duck use during spring migration. Multiple factors related to duck use at local and landscape scales, such as wetland area, vegetation abundance, and number of wetlands in the surrounding landscape. Among semi-permanent wetlands, local factors within wetlands were more important than landscape factors in determining duck use. Collectively, our findings suggest semi-permanent wetlands within the PPR play a key role in transitioning birds from wintering areas to breeding areas and that management of semi-permanent wetlands should promote interspersion of emergent vegetation and open water and growth of submersed aquatic plants to improve their function for migrants. © 2021 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

鸿雁迁徙对停歇地的选择特征

建立合理的湿地水鸟保护地是缓解水鸟栖息地丧失和种群下降的重要手段。以往的保护地设计中,由于越冬地和和繁殖地水鸟停留时间长、种群数量大,受到较多的关注。分析湿地水鸟对停歇地的选择偏好,掌握停歇地的自然条件和人类活动特征可为水鸟保护网络优化和保护地管理提供决策依据。而在水鸟迁徙过程中,停歇地作为保护网络的重要节点也发挥了重要作用。因此选择鸿雁为伞护种,获取了29只鸿雁项圈追踪数据,分析蒙古国Khukh湖-中国东北鸭绿江口秋季迁徙路线对停歇地生境选择偏好,识别了鸿雁在湿地周边不同距离梯度下的活动频率变化。根据鸿雁停歇数据共识别停歇地63处,以此为基础分析停歇的自然条件和人类活动因素特征。结果表明,鸿雁除选择湖泊和沼泽为停歇地外,周边250m内的裸地和草地也是重要栖息地;当鸿雁停歇地人类活动较少时,鸿雁倾向于选择土壤肥沃、食物丰富区,而人类活动强度加大时,栖息地植被条件提高能够为鸿雁提供遮避条件,也吸引了更多鸿雁停歇。研究建议,在水鸟迁徙重要廊道区应增加水鸟停歇地保护区,保护区的设计应根据关键保护对象活动频率加强对湿地周边的栖息地保护,减少水滨人类活动对鸿雁停歇的负面影响;在人类活动强度较大的地区设立水鸟保护地,还应加强对植被的保护,在水鸟利用频率较高的停歇地周边进行植被修复。     

Variation in the Diet of Ducks During Spring Migration

Because management practices that promote the production of plant foods may differ from management practices that promote the production of aquatic invertebrates, a thorough understanding of the diet is needed to develop management strategies for various stages of the annual cycle for dabbling and diving ducks. Diet of dabbling (tribe Anatini) and diving (tribe Aythyini) ducks during breeding, autumn migration, and winter has been documented. Our goal was to estimate and compare the diet of blue-winged teal (Spatula discors), gadwall (Mareca strepera), mallard (Anas platyrhyncos), lesser scaup (Aythya affinis), and ring-necked duck (Aythya collaris) during spring migration in the Mississippi Flyway in the United States and evaluate variation among species. We collected 919 ducks for diet analysis from multiple wetlands at 6 sites across 4 states during the spring migration of 2006 and 2007. We collected ≥10 individuals of each species at each of the 6 study sites except we collected only 1 gadwall at the Scioto River site and 2 lesser scaup at the Cache River site. We detected that the proportion of plant and animal material in foods of each spring migrating duck species was in general intermediate of that found in wintering and breeding birds. Furthermore, the proportion of plant and animal material in the diet of species varied even among closely related species, indicating species are partitioning food sources along a protein-carbohydrate gradient during spring migration. We recommend that resources for ducks be managed to provide diverse wetlands to support the varied diets of even closely related species. © 2021 The Wildlife Society.     

Spatiotemporal dynamics of duck harvest distributions in the Central and Mississippi flyways, 1960–2019

Geographical distributions of waterfowl exhibit annual variation in response to spatiotemporal variation in weather conditions, habitat availability, and other factors. Continuing changes in climate and land use could lead to persistent shifts of waterfowl distributions, potentially causing a mismatch with habitat conservation planning, wetland restoration efforts, and harvest management decisions informed by historical distributions. We used band recoveries and harvest records (i.e., hunter-harvested wings) from the United States Fish and Wildlife Service Waterfowl Parts Collection Survey as indices of duck distribution in autumn and winter, and quantified intra-annual, interannual, and interspecific variation in their geographic distributions across 6 decades (1960–2019) for 15 duck species in the Central and Mississippi flyways in North America. Specifically, we tested for annual and decadal shifts in mean latitude and longitude of recoveries for each month (Oct–Jan) by species and taxonomic guild (i.e., dabbling, diving ducks). Overall, species varied in the extent, timing, and sometimes direction, of distributional change in recoveries. From 1960–2019, mean recovery locations for dabbling ducks shifted south 105–296 km in October and 27 km in November (wings only), whereas mean latitudes shifted north 144–234 km in December and 186–301 km in January. Mean recovery locations for diving ducks shifted north 162 km in October (wings only), 84–173 km in December, and 66–120 km in January, but shifted 99–512 km south in November. Shifts in longitude were less consistent between guilds and data types. Finally, distributional change rarely accelerated during recent decades, except for southward shifts of band recoveries of diving ducks in November and northward shifts of band and wing recoveries of dabbling ducks in January. Although anecdotal accounts of large-scale northward shifts in duck distributions are prolific in the land management and hunting communities, our data demonstrate more subtle shifts that vary considerably by species and month. Observed changes in recovery distributions could necessitate changes in timing of habitat management practices throughout the Central and Mississippi flyways and may result in fewer hunting and recreational opportunities for some species in southern states. Quantifying patterns of historical change is a necessary first step to understanding temporal and interspecific variation in waterfowl distributions, which will help with landscape-scale conservation and management efforts in the future and enable effective communication to core constituencies regarding ongoing changes and their implications for recreational engagement.     

Weather-Related Indices of Autumn– Winter Dabbling Duck Abundance in Middle North America

ABSTRACT Research on effects of key weather stimuli influencing waterfowl migration during autumn and winter is limited. We investigated relationships between changes in relative abundances of mallard (Anas platyrhynchos) and other dabbling ducks (Anas spp.) and weather variables at midlatitude locations in North America. We used waterfowl survey data from Missouri Conservation Areas and temperature and snow cover data from the Historical Climatology Network to evaluate competing models to explain changes in relative abundance of ducks in Missouri, USA, during autumn-winter, 1995–2005. We found that a cumulative weather severity index model (CumulativeWSI; calculated as mean daily temp - degrees C + no. of consecutive days with mean temp ≤ 0° C + snow depth + no. of consecutive days with snow cover) had the greatest weight of evidence in explaining changes in relative abundance of ducks. We concluded the CumulativeWSI reflected current and cumulative effects of ambient temperatures on energy expenditure by ducks, and snow cover and wetland icing, on food availability for ducks. The CumulativeWSI may be useful in determining potential changes in autumn-winter distributions of North American waterfowl given different climate change projections and associated changes in habitat conservation needs. Future investigations should address interactions between CumulativeWSI and landscape habitat quality, regional waterfowl populations, hunter harvest, and other anthropogenic influences to increase understanding of waterfowl migration during autumn-winter.     

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.     

Do captive waterfowl alter their behaviour patterns during their flightless period of moult?

Many different behavioural changes have been observed in wild waterfowl during the flightless stage of wing moult with birds frequently becoming inactive and reducing time spent foraging. Increased predation risk, elevated energetic demands of feather re-growth and restriction of foraging opportunities are thought to underlie these changes. By studying captive populations of both a dabbling and a diving duck species at the same site, we determined whether captive birds would reflect the behavioural responses of wild waterfowl to moult. The time-budgets of 42 Common Eiders, Somateria mollissima, (a diving duck) and 18 Garganeys, Anas querquedula, (a dabbling duck) were recorded during wing moult (July–August) and non-moult (January) with behaviour recorded under six categories. Despite captivity providing a low predation risk and constant access to food, birds altered their behaviour during the flightless period of wing moult. Time allocated to foraging and locomotion decreased significantly during moult compared to non-moult periods, while resting time increased significantly. Moulting Eiders underwent a greater reduction in time spent foraging and in locomotion compared with Garganeys, which is likely to be in response to a higher energetic cost of foraging in Eiders. It is possible that increased resting in both diving and dabbling ducks reduces their likelihood of detection by predators, while allowing them to remain vigilant. We demonstrate that there is much potential for using captive animals in studies that can augment our knowledge of behaviours of free-living conspecifics, the former being a hitherto under-exploited resource.     

Waterbird communities and seed biomass in managed and reference‐restored wetlands in the Mississippi Alluvial Valley

The Natural Resources Conservation Service (NRCS) commenced the Migratory Bird Habitat Initiative (MBHI) in summer 2010 after the April 2010 Deepwater Horizon oil spill in the Gulf of Mexico. The MBHI enrolled in the program 193,000 ha of private wet‐ and cropland inland from potential oil‐impaired wetlands. We evaluated waterfowl and other waterbird use and potential seed/tuber food resources in NRCS Wetland Reserve Program easement wetlands managed via MBHI funding and associated reference wetlands in the Mississippi Alluvial Valley of Arkansas, Louisiana, Mississippi, and Missouri. In Louisiana and Mississippi, nearly three times more dabbling ducks and all ducks combined were observed on managed than reference wetlands. Shorebirds and waterbirds other than waterfowl were nearly twice as abundant on managed than referenced wetlands. In Arkansas and Missouri, managed wetlands had over twice more dabbling ducks and nearly twice as many duck species than reference wetlands. Wetlands managed via MBHI in Mississippi and Louisiana contained ≥1.3 times more seed and tuber biomass known to be consumed by waterfowl than reference wetlands. Seed and tuber resources did not differ between wetlands in Arkansas and Missouri. While other studies have documented greater waterbird densities on actively than nonmanaged wetlands, our results highlighted the potential for initiatives focused on managing conservation easements to increase waterbird use and energetic carrying capacity of restored wetlands for waterbirds.     

Occupancy Patterns of Breeding American Black Ducks

Occupancy patterns can assist with the determination of habitat limitation during breeding or wintering periods and can help guide population and habitat management efforts. American black ducks (Anas rubripes; black ducks) are thought to be limited by habitat and food availability during the winter, but breeding sites may also limit the size or growth potential of the population. The Canadian Wildlife Service conducts an annual breeding waterfowl survey that we used to explore the hypothesis that black duck carrying capacity is limited by wetlands available for breeding in Québec, Canada. We applied single-visit, multi-species occupancy models to the 1990–2015 population survey data to determine if there was evidence the black duck population was limited by breeding habitat. Using a dynamic (multi-season) occupancy modeling approach, we estimated latent occupancy (occupancy accounting for imperfect detection) of black ducks and then used latent occupancy estimates to derive occupancy, colonization, and extirpation rates. We jointly modeled the occupancy dynamics of black ducks and other duck species in wetlands where both species were present. Throughout the duration of the survey, 44% of wetlands were never observed to be occupied by black ducks. Occupancy models showed wetland size was positively associated with occupancy at the first time step (initial occupancy) and colonization. All 2-species models indicated initial black duck occupancy, persistence (continued occupancy), and colonization were positively associated with the presence of a second species. Colonization rate over the 26-year period ranged from 7% to 27% across all models. Extirpation rates were similar and were constant through time within each model. Low occupancy rates, combined with approximately equal colonization and extirpation rates, suggest there are available wetlands for breeding black ducks in their core breeding area. If breeding habitats are not saturated, this suggests migration or wintering areas may be more limiting to black duck population abundance. © 2019 The Wildlife Society.     

Winter weather and waterfowl surveys in north-western Ontario, Canada

Abstract Aim An analysis is presented to examine whether variation in breeding waterfowl estimates can be explained by weather patterns prior to annual surveys. Location The location of the study is north‐western Ontario, Canada. Methods Annual, systematic survey data for breeding waterfowl are available from the 1950s to the present for north‐western Ontario. Regional monthly climate data for this area were compiled using weather data derived from interpolated annual climate surfaces. These data were analysed using stepwise multiple linear regression for each species and for waterfowl functional groups to assess whether monthly climate data accounted for some of the variation in waterfowl numbers. Results For all dabbling ducks pooled, 12% of the variation in annual abundance was explained by April temperatures, with more dabbling ducks observed in years when April was relatively cool. For diving ducks, 23% of the variation in pooled abundance was explained by April temperatures and February precipitation, where more diving ducks were observed in years when February had relatively less precipitation and April was cool. Patterns for individual species varied. Main conclusions Mean monthly weather data for months prior to surveys explained some of the variation in numbers of waterfowl observed in annual surveys. This suggests that future incorporation of weather data into waterfowl population models may help refine population estimates.     

Waterfowl on weather radar: applying ground-truth to classify and quantify bird movements

ABSTRACT Local and migratory movements aloft have important implications for the ecology and conservation of birds, but are difficult to quantify. Weather surveillance radar (WSR) offers a unique tool for observing movements of birds, but until now has been used primarily to address broad taxonomic questions. Herein, we demonstrate how natural history information and ground‐truthing can be used to answer quantitative and taxon‐specific questions regarding bird movements on WSR. We found that super‐resolution Level II data from the National Oceanic and Atmospheric Administration's mass storage system was the most effective format and source of WSR data, and that several software packages were needed for thorough analysis of WSR data. Using WSR, we identified potential movements of birds emigrating from a waterfowl stopover area in Illinois in fall (1 September–31 December) 2006 and 2007. We compared spatial and temporal patterns of these movements to the natural history of taxa occupying the source habitat and classified these radar targets as dabbling ducks (tribe Anatini). A portable X‐band radar measured the cruising heights of ducks at 400–600 m. During fall 2008, we conducted ground‐truthing with a thermal infrared camera to enumerate birds passing over our field site during nocturnal migration events. This estimate of bird density, paired with an associated sample of WSR echo strength, provided a mean radar cross section the same as dabbling ducks (112.5 cm²) and supported our natural‐history‐based classification. Thermal infrared‐estimated duck densities explained most of the variation (R²= 0.91) in WSR echo strength across seven migration events of varying intensities, suggesting that radar cross sections of dabbling ducks and WSR reflectivity can be used to estimate duck numbers in other comparable contexts. Our results suggest that careful investigation of the spatial and temporal patterns of movements on radar, along with field‐based ground‐truthing, can be used to study and quantify the movements of specific bird taxa.     

Spatial and temporal changes in prevalence of a cloacal cestode in wintering waterfowl along the Gulf Coast of Texas

The cloacal cestode Cloacotaenia megalops is one of the most common helminths of waterfowl. We investigated the effect of this parasite on the body condition of wintering waterfowl populations and compared prevalence among age-sex classes, over time and between habitat types on the upper Gulf Coast of Texas (USA) from October 1986-February 2000. Greater than 9,500 birds of 25 waterfowl species were examined for the parasite. There was no statistical difference (P > 0.05) in body condition between birds with and without the parasite. Average prevalence was lowest for geese (mean = 3.7%) versus 21 to 71% in duck species. Average prevalence was similar (P = 0.81) between diving ducks (mean = 46.9%) and puddle ducks (mean = 43.9%). Prevalence varied among age-sex classes and was related to sex rather than age. Variation among age-sex classes suggests differences in diet between sexes of duck species on the wintering grounds. There was no evidence for declining prevalence over the wintering period. Prevalence differed (P < 0.05) between collection sites, and thereby habitat types, for several species. Temporal trends indicate stable prevalence of C. megalops for diving ducks and increasing prevalence for puddle ducks. The increasing trend for puddle ducks may indicate declining habitat conditions resulting in increased exposure to the intermediate ostracod host.     

The Effect of Sea Level Rise on Dabbling Duck Energetic Carrying Capacity

Waterfowl migrating and overwintering in the Atlantic Flyway depend on adequate availability of wetland plant communities to survive winter and fuel reproduction in the subsequent breeding season. Energetics models are the primary tool employed by conservation planners to estimate energetic carrying capacity based on energy supply and demand in different wetlands to assist with effective habitat conservation. Coastal impoundments have been used to provide a consistent, annual source of energy for migrating and wintering waterfowl. But few studies have attempted to comprehensively assess the relative value of managed coastal impoundments compared with unmanaged tidal salt marshes to wintering waterfowl in the Mid-Atlantic region with further consideration to the effect of sea level rise changing availability. We estimated biomass and energy of preferred foods for 5 dabbling duck species in 7 impoundments and 3 tidal salt marshes over winter by collecting soil core (n = 1,364), nekton (n = 426), and salt marsh snail (Melampus spp.; n = 87) samples in October, January, and April 2011–2013. Food-energy density was greater in freshwater impoundments for nearly all dabbling ducks (range = 183,344–562,089 kcal/ha), and typically greater in brackish impoundments (range = 169,665–357,160 kcal/ha) than most tidal salt marsh communities (range = 55,693–361,429 kcal/ha), whereas mudflat (range = 96,223–137,473 kcal/ha) and subtidal (range = 55,693–136,326 kcal/ha) communities typically contained the least energy. Extrapolating to the state level, we estimated 7.60 × 10⁹–1.14 × 10¹⁰ kcal available within a 16-km buffer from the Delaware Bayshore, depending on species. Combining estimates for daily energy expenditure and food energy, we estimated 2.86 × 10⁷–7.06 × 10⁷ duck energy days currently available to dabbling ducks over winter. We estimated that in the next century, dabbling duck carrying capacities are likely to decrease under all but the most conservative sea level rise scenarios because of the gradual replacement of land-cover types that provide high energy density (i.e., low marsh, high marsh communities) with those that provide low energy density (i.e., subtidal, mudflat communities). Coastal impoundments in Delaware, USA, will provide increasingly important habitat for wintering dabbling ducks in the coming decades provided they are properly maintained and retain their current energetic density because they will contain a growing proportion of the available duck energy days on the landscape. Our research will assist managers in meeting target population goals for dabbling ducks in Delaware and the Mid-Atlantic region by highlighting key differences in the function and value of various wetlands. © 2021 The Wildlife Society.     

Patterns of cryptic host specificity in duck lice based on molecular data

Documenting patterns of host specificity in parasites relies on the adequate definition of parasite species. In many cases, parasites have simplified morphology, making species delimitation based on traditional morphological characters difficult. Molecular data can help in assessing whether widespread parasites harbour cryptic species and, alternatively, in guiding further taxonomic revision in cases in which there is morphological variation. The duck louse genus Anaticola (Phthiraptera: Philopteridae), based on current taxonomy, contains both host‐specific and widespread species. Mitochondrial and nuclear DNA sequences of samples from this genus were used to document patterns of host specificity. The comparison of these patterns with morphological variations in Anaticola revealed a general correspondence between the groups identified by DNA sequences and morphology, respectively. These results suggest that a more thorough taxonomic review of this genus is needed. In general, the groups identified on the basis of molecular data were associated with particular groups of waterfowl (e.g. dabbling ducks, sea ducks, geese) or specific biogeographic regions (e.g. North America, South America, Australia, Eurasia).     

Condition Bias of Decoy-Harvested Light Geese During the Conservation Order

Evidence that decoy harvest techniques primarily remove individuals of poorer body condition is well established in short-lived duck species; however, there is limited support for condition bias in longer-lived waterfowl species, such as geese, where decoy harvest is considered primarily additive because of their high natural survival rates. We evaluated support for the harvest condition bias hypothesis of 2 long-lived waterfowl species, the lesser snow goose (Anser caerulescens caerulescens) and Ross's goose (Anser rossii). We used proximate analysis to quantify lipid and protein content of lesser snow and Ross's geese collected during the Light Goose Conservation Order (LGCO) in 2015 and 2016 during spring migration in Arkansas, Missouri, Nebraska, and South Dakota, USA. In each state, LGCO participants collected birds using traditional decoy techniques and we collected birds from the general population using jump-shooting tactics. Total body lipid content in both lesser snow and Ross's geese varied with age, region of harvest, and harvest type (decoy or jump-shooting). On average, adult lesser snow and Ross's geese harvested over decoys had 60 g and 41 g, respectively, fewer lipids than conspecifics collected using jump-shooting. We observed lower lipid reserves in decoy-shot geese in all 4 states sampled despite general gains in lipid reserves as migration chronology progressed. Our data support that the harvest condition bias extends to longer-lived waterfowl species and during a life-history event (spring migration) in which harvest is not normally observed. In the case of overabundant light geese, the disproportionate harvest of poorer-conditioned lesser snow and Ross's geese may serve as an additional challenge against any realized effects of harvest to reduce the population, in addition to extremely low harvest rates. © 2019 The Wildlife Society.     

Effect of wind energy development on breeding duck densities in the Prairie Pothole Region

Industrial wind energy production is a relatively new phenomenon in the Prairie Pothole Region and given the predicted future development, it has the potential to affect large land areas. The effects of wind energy development on breeding duck pair use of wetlands in proximity to wind turbines were unknown. During springs 2008–2010, we conducted surveys of breeding duck pairs for 5 species of dabbling ducks in 2 wind energy production sites (wind) and 2 paired reference sites (reference) without wind energy development located in the Missouri Coteau of North Dakota and South Dakota, USA. We conducted 10,338 wetland visits and observed 15,760 breeding duck pairs. Estimated densities of duck pairs on wetlands in wind sites were lower for 26 of 30 site, species, and year combinations and of these 16 had 95% credible intervals that did not overlap zero and resulted in a 4–56% reduction in breeding pairs. The negative median displacement observed in this study (21%) may influence the prioritization of grassland and wetland resources for conservation when existing decision support tools based on breeding-pair density are used. However, for the 2 wind study sites, priority was not reduced. We were unable to directly assess the potential for cumulative impacts and recommend long-term, large-scale waterfowl studies to reduce the uncertainty related to effects of broad-scale wind energy development on both abundance and demographic rates of breeding duck populations. In addition, continued dialogue between waterfowl conservation groups and wind energy developers is necessary to develop conservation strategies to mitigate potential negative effects of wind energy development on duck populations. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.