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The miniaturization of Global Positioning Systems (GPS) transmitters is providing insights into the ecology and management of migratory bird species at biologically‐relevant spatial scales. However, transmitters and their attachment methods could bias inferred behaviors, demographic rates, and resulting management decisions. We evaluated the effects of external harness‐style GPS transmitters by comparing direct harvest rates, winter dispersal distances, and subsequent harvest distributions of mallards (Anas platyrhynchos) equipped with GPS transmitters (n = 443) to a tarsal banded‐only control group (n = 1,123) captured in western Tennessee during winters 2019–2022. We found that transmitter‐marked mallards had similar harvest rates, winter dispersal distances, and harvest distributions as banded‐only mallards. Time between capture and harvest predicted dispersal distances but there was no effect of marker type. Specifically, the average time from capture to harvest was 30 (SE = 2) and 31 (SE = 3) days for banded‐only and transmitter‐marked mallards, respectively. Harvest rate (h ) was only 2.2% greater for transmitter‐marked mallards compared to banded‐only mallards overall, but GPS transmitters affected harvest susceptibility of juveniles (∆hjuv = 14.5%). Based on harvest rates and dispersal distances between transmitter‐marked and banded‐only cohorts, we suggest 7‐ to 10‐day data censoring periods may be warranted, especially for juveniles, as mallards acclimate to GPS transmitters. Overall, we concluded that modern harness‐style GPS transmitters provided reliable information of wintering mallard space use, movements, and harvest mortality and can be used to inform ecology and management of wintering mallards and other dabbling ducks. Future studies should evaluate effects of harness‐style GPS transmitters for other species and during different portions of dabbling ducks' life cycle, such as migration or nesting, when they may experience greater adverse effects. [ABSTRACT FROM AUTHOR]

The energy derived from available foods is an important factor used in conservation planning for migratory species. Estimating true metabolizable energy (TME) of available foods has become a common method for resource managers to increase reliability in energetic carrying‐capacity estimates. Lesser scaup (Aythya affinis; hereafter scaup), have experienced a population decline concurrent with suspected decreases in foraging habitat quality and quantity at spring stopover sites in the upper Midwest, USA. Unfortunately, few TME estimates are available for common diet items of scaup. We estimated nitrogen‐adjusted TME (TMEN) of 5 common foods of scaup by conducting feeding trials on wild females and males. True metabolizable energy varied by food taxa, but not by pretrial body mass or sex. Mean TMEN (kcal/g[dry] ± SE) was greatest for wild millet (Echinochloa crus‐galli; 2.20 ± 0.14), followed by chironomids (Chironomus spp.; 1.41 ± 0.49), amphipods (Gammarus spp.; 1.33 ± 0.23), planorbid snails (Planorbidae; 0.17 ± 0.07), and fingernail clams (Sphaeriidae; −0.79 ± 0.27). Our results, combined with scaup diet literature indicated that the management of spring staging areas for high‐energy invertebrates (i.e., chironomids and amphipods) would provide improved opportunity for energy acquisition during migration. Further study could help determine if the acclimation of scaup to particular diets, especially bivalves, increases their TMEN values. [ABSTRACT FROM AUTHOR]

Extreme climatic events (ECEs) can have profound impacts on individual fitness, affecting survival directly or indirectly. Late winter ECEs may be especially detrimental to fitness due to limited food resources and increased energetic requirements during this time. A polar vortex disruption ECE descended upon the mid-continental United States during February 7–20, 2021 with temperatures as low as −29°C in areas concurrent with ongoing research on Anas platyrhynchos (Mallard) movement ecology and survival in Arkansas, Louisiana, and Tennessee, United States spanning winters 2019–2022. Therefore, we opportunistically evaluated the effects of individual characteristics and latitude on daily survival during the ECE. We extended the survival analysis to March to test for lasting effects of the ECE on survival. We tracked 181 Global Positioning System (GPS)-marked A. platyrhynchos during February 2020, 256 in February 2021, and 324 in February 2022. We documented 22 mortalities during the February 2021 ECE (i.e. 9%), but only 6 mortalities during February 2020 (i.e. 2%) and 2022 (i.e. 1%) when conditions were average. February survival (e.g. 28-day survival) during the ECE was 0.908 (85% CI: 0.879–0.937) but was 0.982 (85% CI: 0.973–0.991) during the 2 non-ECE Februaries. The ECE effect on survival was isolated to February and did not affect March survival. Anas platyrhynchos was 5.4 times more likely to die during the ECE in 2021 compared to non-ECE Februaries. Although large-bodied waterfowl appear cold-tolerant and less sensitive to polar vortex disruptions compared to smaller-bodied passerines, direct mortalities can occur if conditions are severe enough and persist, highlighting the need to consider the influence of ECEs on common, seemingly robust species in future global climate change scenarios. [ABSTRACT FROM AUTHOR]

Our aim was to describe shifts in autumn and winter harvest distributions of three species of dabbling ducks (blue‐winged teal [Spatula discors], mallard [Anas platyrhynchos], and northern pintail [Anas acuta]) in the Central and Mississippi flyways of North America during 1960–2019. We measured shifts in band recovery distributions corrected for changes in hunting season dates and zones by using kernel density estimators to calculate 10 distributional metrics. We then assessed interannual and intraspecific variation by comparing species‐specific changes in distributional metrics for 4 months (October–January) and three geographically based subpopulations. During 1960–2019, band recovery distributions shifted west‐ and southwards (blue‐winged teal) or east‐ and northwards (mallard and northern pintail) by one hundred to several hundred kilometers. For all three species, the broad (95% isopleth) and core distributions (50% isopleth) showed widespread decreases in overlap and increases in relative area compared to a 1960–1979 baseline period. Shifts in band recovery distributions varied by month, with southward shifts for blue‐winged teal most pronounced in October and northward shifts for mallard and northern pintail greatest during December and January. Finally, distributional metric response varied considerably among mallard subpopulations, including 2–4‐fold differences in longitude, latitude, and overlap, whereas differences among subpopulations were minimal for blue‐winged teal and northern pintail. Our findings support the popular notion that winter (December–January) distributions of duck species have shifted north; however, the extent and direction of distributional changes vary among species and subpopulations. Long‐term distributional changes are therefore complex and summarizing shifts across species, months, or subpopulations could mask underlying finer‐scale patterns that are important to habitat conservation and population management. A detailed understanding of how species distributions have changed over time will help quantify important drivers of species occurrence, identify habitat management options, and could inform decisions on where to focus conservation or restoration efforts. [ABSTRACT FROM AUTHOR]

Spring migration is an energetically demanding event that can impact nutrient dynamics of individuals during the breeding season through carry-over effects. Limited food availability at spring stopover areas may have cross-seasonal effects that adversely impact waterfowl populations. We collected 161 Green-winged Teal (Anas crecca Linnaeus, 1758; hereafter Teal) throughout the Illinois River Valley, USA, during February--April of 2016-2018 and estimated body condition using three condition indices (scaled mass index, scaled wing index, body-size index) for comparison with carcass lipid and protein values. Lipids were 18.3% (95% CI = 1.0%-38.5%) and 21.6% (95% CI = 4.8%-41.0%) greater at locations with moderate (250-600 kg/ha) and high (>600 kg/ha) moist-soil seed densities, respectively, than low moist-seed density ( Key words: Anas crecca, Green-winged Teal, body condition, food availability, Illinois, proximate analysis, spring migration. La migration printaniere est un evenement exigeant du point de vue energetique qui peut avoir une incidence sur la dynamique des nutriments des individus durant la periode de reproduction, par l'entremise d'effets reportes. Une faible disponibilite de nourriture dans les aires de repos printanieres pourrait avoir des effets inter-saisonniers qui ont une incidence negative sur les populations de sauvagine. Nous avons preleve 161 sarcelles d'hiver (Anas crecca Linnaeus, 1758; ci-apres [much less than] sarcelle [much greater than]) a la grandeur de la vallee de la riviere Illinois (Etats-Unis) de fevrier a avril 2016 a 2018 et estime leur embonpoint en utilisant trois indices d'embonpoint (indice de masse mise a l'echelle, indice des ailes mises a l'echelle et indice de taille du corps) a des fins de comparaison avec les contenus en lipides et en proteines des carcasses. Les contenus en lipides etaient 18,3% (IC 95 % = 1,0 % -38,5 %) et 21,6% (IC 95 % = 4,8 % - 41,0 %) plus grands dans les endroits caracterises par des densites de graines dans le sol humide moderees (250-600 kg/ha) et elevees (>600 kg/ha), respectivement, que dans les sites de faible densite ( Mots-cles : Anas crecca, sarcelle d'hiver, embonpoint, disponibilite de nourriture, Illinois, analyse immediate, migration printaniere., Introduction Migration is a critical period for long-distance migratory birds due to energetic demands of flight, courtship, pair bonding, and nutrient deposition coinciding with extreme environmental stochasticity and probable food [...]

Public lands managed for wildlife frequently provide various forms of sanctuary to increase residency times and allow access to energetic and other habitat resources for waterfowl. The influence of sanctuary type and disturbance regime on resource use and fine-scale movements of waterfowl has not been investigated extensively using currently available transmitter technologies. We examined mallard (Anas platyrhynchos) use of various types of waterfowl sanctuary and non-sanctuary areas in the Mississippi Alluvial Valley region of eastern Arkansas, USA, during winters of 2019-2021. We deployed 105 global positioning system transmitters on mallards at 4 closed-access spatial sanctuaries on or adjacent to Dale Bumpers White River National Wildlife Refuge.We used hourly transmitter locations to examine mallard use of public sanctuary areas, public hunt areas, and private lands using integrated step selection analysis. Public sanctuary areas provided varying levels of protected status, public hunt areas allowed for varying levels of hunting intensity by duck hunters, and private lands were open to waterfowl hunting and other forms of private uses but may or may not have been hunted at any specific frequency. Mallards selected spatial sanctuary and avoided public hunt areas, other sanctuary types, and private lands during the day. In contrast, mallards selected for private lands over spatial sanctuary at night. Mallards tended to avoid areas that allowed duck hunting or used them during the night when risk of harvest mortality was removed. After the hunting season closed, mallards began using areas that previously allowed duck hunting during the day, suggesting that risk was the primary factor influencing site use. Moreover, mallards were 1.6 times more likely to use public daily hunt areas and 2.1 times more likely to use private lands potentially open to hunting during the day than spatial sanctuary 2 weeks after the close of duck hunting season in February. Spatial sanctuaries appear more effective in influencing mallard use than temporal sanctuaries or inviolate sanctuaries, which are commonly used by state and federal agencies. Partial daily, daily, or activity-specific (e.g., no hunting past noon, no hunting 3 days/week, no waterfowl hunting) closures to encourage mallard use of temporal sanctuaries do not appear to reduce the perceived harvest-related risk to mallards enough for them to view these areas as accessible or significantly increase their use. [ABSTRACT FROM AUTHOR]

The spatiotemporal allocation of activity is fundamental to how organisms balance energetic intake and predation risk. Activity patterns fluctuate daily and seasonally, and they are proximately affected by exogenous and endogenous conditions. For birds, flight activity is often necessary for relocating between foraging patches but is energetically expensive and can increase mortality risk. Hunted species may have to adjust their behavior and activity patterns to minimize anthropogenic mortality risk. We used hourly locations from 336 GPS-marked mallards Anas platyrhynchos to examine how hunting pressure affected flight activity in response to weather conditions and habitat availability during winter in western Tennessee, USA. Mallards were more likely to fly during crepuscular times, particularly dusk, across winter months. Mallards conducted more flights after shooting hours when habitat availability increased during open hunting season; conversely, mallard flights decreased with increasing habitat availability when hunters were present on the landscape. Mallards were least active during periods open to hunting. However, indicators of approaching inclement weather (i.e. increased wind speed, precipitation, and decreasing barometric pressure) increased flights during periods open to hunting. Mallard flights decreased at lower temperatures except when hunting season was closed, wherein mallards increased nighttime flights. Flight activity was directly influenced by hunting disturbance which constrained when and how mallards reacted to environmental and habitat conditions. An understanding of the temporal shifts in waterfowl flight patterns can be used by natural resource managers to better manage stakeholder satisfaction and expectations. [ABSTRACT FROM AUTHOR]

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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. [ABSTRACT FROM AUTHOR]

Waterfowl are housed in captivity for research studies that are infeasible in the wild. Accommodating the unique requirements of semi-aquatic species in captivity while meeting experimental design criteria for research questions can be challenging and may have unknown effects on animal health. Thus, testing and standardizing best husbandry and care practices for waterfowl is necessary to facilitate proper husbandry and humane care while ensuring reliable and repeatable research results. To inform husbandry practices for captive-reared and wild-caught lesser scaup (Aythya affinis ; hereafter, scaup), we assessed body mass and fat composition across two different aspects of husbandry, source population (captive-reared or wild caught), and housing densities (birds/m2). Our results suggest that housing scaup at low densities (≤0.6 m2/bird, P  = 0.049) relative to other species can minimize negative health effects. Captive-reared scaup were heavier (P  = 0.027) with greater body fat (P  < 0.001) and exhibited fewer signs of stress during handling than wild-caught scaup. In our experience, scaup which are captive-reared from eggs collected in the wild were better for long-term captivity studies as they maintained body mass between and recovered lost body mass following trials. Researchers would benefit from carefully evaluating the tradeoffs of using short- and long-term captive methods on their research question before designing projects, husbandry practices, and housing facilities for waterfowl. [ABSTRACT FROM AUTHOR]