Mississippi Flyway Research Articles

Postbreeding ecology of wood ducks in the Illinois River Valley

AbstractThe wood duck (Aix sponsa) consistently ranks within the top 5 harvested duck species for both Illinois and the Mississippi Flyway. While substantial research has been done on wood ducks, especially their breeding ecology, few studies have investigated the postbreeding ecology of the species. We captured and marked wood ducks with either a very high frequency (VHF) radio transmitter or a solar‐charged global system of mobile communication (GSM) transmitter during the postbreeding period from August through September 2018–2020. Capture locations were within the La Grange Pool of the Illinois River extending from near Pekin, Illinois to the La Grange Lock and Dam near Meredosia, Illinois, USA. We used conventional radio‐telemetry techniques to track wood ducks to determine cover type use, home range size, daily movement patterns, survival, and migration chronology. Home range size (95% minimum convex polygon) for wood ducks averaged 6,820 ± 572 ha (SE) and we did not find evidence for a difference by age, sex, or transmitter type. Daily movement distance in August (2,031 ± 51 m) was similar to daily movement distance in September (1,922 ± 44 m), but daily movement distances for August and September were less than daily movement distance for October (3,509 ± 53 m) and November (3,347 ± 106 m). Wood ducks primarily used wetlands with woody (45.0%) and emergent vegetation (40.4%), and the most commonly used wetland types by wood ducks were impounded wetlands (53.8%), lakes (17.6%), and ponds (10.7%). Model‐derived survival during the postbreeding period was 0.79 (95% CI = 0.74–0.84). Daily survival was positively related to increased river level and had a mean increase of 4.06 ± 0.67% for every 0.3‐m increase in the Illinois River level at low river levels (1.5–3.0 m) and a mean increase of 1.38 ± 0.32% for every 0.3‐m increase in the Illinois River level at high river levels (4.0–5.5 m). Average departure date of wood ducks leaving the Illinois River Valley was 27 October (range =13 August–15 December), and adult male wood ducks left the study area 11–16 days earlier than the other age and sex cohorts (H2 = 11.6, P = 0.01). Providing additional waterfowl sanctuaries that contain wooded wetlands, especially in years of low river levels, may increase survival for wood ducks during the postbreeding period.

Long-term changes in autumn-winter harvest distributions vary among duck species, months, and subpopulations.

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.

Surveillance for highly pathogenic avian influenza A (H5N1) in a raptor rehabilitation center-2022.

An ongoing, severe outbreak of highly pathogenic avian influenza virus (HPAI) A H5N1 clade 2.3.4.4b has been circulating in wild and domestic bird populations throughout the world, reaching North America in 2021. This HPAI outbreak has exhibited unique characteristics when compared to previous outbreaks. The global distribution of disease, prolonged duration, extensive number of species and individual wild birds affected, and the large impact on the global poultry industry have all exceeded historical impacts of previous outbreaks in North America. In this study, we describe the results of HPAI surveillance conducted at The Raptor Center, a wildlife rehabilitation hospital at University of Minnesota (Saint Paul, MN, U.S.A.), from March 28th-December 31, 2022. All wild raptors admitted to the facility were tested for avian influenza viruses using polymerase chain reaction (PCR) testing. All non-negative samples were submitted to the United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) National Veterinary Services Laboratories for confirmatory HPAI testing and genetic sequencing. During the study period, 996 individual birds representing 20 different species were tested for avian influenza, and 213 birds were confirmed HPAI positive. Highly pathogenic avian influenza surveillance conducted at The Raptor Center contributed 75% of the HPAI positive raptor detections within the state of Minnesota, located within the Mississippi flyway, significantly augmenting state wildlife surveillance efforts. The viral genotypes observed in birds sampled at The Raptor Center were representative of what was seen in wild bird surveillance within the Mississippi flyway during the same time frame. Wildlife rehabilitation centers provide an opportune situation to augment disease surveillance at the human, wildlife and domestic animal interface during ongoing infectious disease outbreaks.

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

AbstractGeographical 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.

North American wintering mallards infected with highly pathogenic avian influenza show few signs of altered local or migratory movements

Avian influenza viruses pose a threat to wildlife and livestock health. The emergence of highly pathogenic avian influenza (HPAI) in wild birds and poultry in North America in late 2021 was the first such outbreak since 2015 and the largest outbreak in North America to date. Despite its prominence and economic impacts, we know relatively little about how HPAI spreads in wild bird populations. In January 2022, we captured 43 mallards (Anas platyrhynchos) in Tennessee, USA, 11 of which were actively infected with HPAI. These were the first confirmed detections of HPAI H5N1 clade 2.3.4.4b in the Mississippi Flyway. We compared movement patterns of infected and uninfected birds and found no clear differences; infected birds moved just as much during winter, migrated slightly earlier, and migrated similar distances as uninfected birds. Infected mallards also contacted and shared space with uninfected birds while on their wintering grounds, suggesting ongoing transmission of the virus. We found no differences in body condition or survival rates between infected and uninfected birds. Together, these results show that HPAI H5N1 clade 2.3.4.4b infection was unrelated to body condition or movement behavior in mallards infected at this location during winter; if these results are confirmed in other seasons and as HPAI H5N1 continues to evolve, they suggest that these birds could contribute to the maintenance and dispersal of HPAI in North America. Further research on more species across larger geographic areas and multiple seasons would help clarify potential impacts of HPAI on waterfowl and how this emerging disease spreads at continental scales, across species, and potentially between wildlife and domestic animals.

Potential economic consequences along migratory flyways from reductions in breeding habitat of migratory waterbirds

The migration of species, often across continents, makes it difficult to quantify the cumulative effects of local- and regional-scale conservation actions. Further, variation in stakeholder interests, differing jurisdictional governance processes, priorities, and monitoring abilities across the migratory range shapes place-specific differences in management actions. These differences may lead management of migratory species to benefit both species and stakeholders in some places more than others. In the case of North American waterfowl, possible reduction of wetland protection in breeding areas may lead to substantive shifts in benefits among stakeholders across their range by adversely affecting recreational viewing and hunting opportunities for these species. To understand possible consequences of wetland loss in the U.S. Prairie Pothole Region, the breeding region for 12 focal species of waterfowl, on the recreation economics for these species, we modeled a causal pathway linking wetland loss in the breeding grounds to changes in duck abundance and then assessed the consequences of that change in abundance on recreational hunting and viewing within migratory flyways. Under a scenario where wetland protections cease, we find annual economic activity associated with recreation may decrease as much as $489 million at the highest levels of predicted wetland loss, the majority of it coming from impacts to viewing behavior in the Mississippi Flyway. The number of hunters may decline by as much as 18,000, leading to $32 million less in annual economic activity. At highest levels of wetland loss, viewing value is expected to decline by more than one-quarter. Lost economic value associated with reductions in recreation in the Mississippi and Central Flyway states is not likely to be overcome by increases in agricultural economic output in drained wetlands of the Prairie Pothole Region. Our analyses indicate local effects of national water policies likely have far-reaching consequences because of the multi-dimensional connections arising from place-specific differences in management action, global and national agricultural economic drivers of crop expansion, and the biotic phenomena of transcontinental avian migration. Reductions in habitat in one location could ramify to economic consequences throughout the continent through connections fostered by migrating waterfowl.

Wetland management practices and secretive marsh bird habitat in the Mississippi Flyway: a review

AbstractManagement regimes on publicly owned freshwater wetlands in the Mississippi Flyway of North America (i.e., Flyway) have historically emphasized waterfowl, but there is limited information on how waterfowl‐focused wetland management affects other wetland‐dependent wildlife. Secretive marsh birds (SMBs) depend on wetlands with emergent vegetation throughout their migratory life cycle and often encounter vegetation and water conditions resulting from waterfowl‐focused management regimes. Thus, there is a need for better understanding of how SMBs are affected by wetland management and the extent to which waterfowl‐focused management regimes provide habitat for SMBs. In this review, we identify the vegetation and water conditions resulting from typical management objectives on freshwater emergent wetlands in the Flyway, review and qualitatively synthesize results from studies that directly evaluate how wetland management practices affect SMBs or their habitat, and assess how the vegetation and water conditions being produced for target species (mainly waterfowl) align with SMB habitat requirements. We searched online databases and used Google Scholar to locate peer‐reviewed literature, technical reports, and graduate theses that pertained to responses of SMBs or their habitat to water‐level manipulation, herbicide application, prescribed fire, disking, mowing, and planting crops. There are several management strategies that complement SMBs and waterfowl, such as reducing cover of woody species and providing flooded emergent vegetation. We also highlight management strategies that may not currently align with SMB life‐cycle needs and suggest adjustments that might promote habitat for SMBs while still achieving waterfowl population objectives. For example, adjusting the dates and duration of spring water‐level drawdowns on a portion of wetlands within a larger complex can provide for spring migrating waterfowl and ensure habitat for migrating and nesting SMBs. Ideally, future studies would address how modifications to management practices affect SMBs and monitor potential effects on waterfowl, resulting in a more holistic approach to wetland management.

Winter range shifts and their associations with species traits are heterogeneous in eastern North American birds

Abstract Many species’ distributions are shifting in response to climate change. Many distributional shifts are predictably poleward or higher in elevation, but heterogeneity in the rate and direction of shifts both within and between species appears to be common. We found high heterogeneity in the trajectory of winter range shifts for 65 species of birds across eastern North America and in the different traits and trait interactions associated with these shifts across the spatial scales we examined. We used data from the Christmas Bird Count to quantify the trajectory of winter latitudinal center of abundance range shifts over 4 decades (1980–2019) for 65 species of songbirds and woodpeckers in North America, both across eastern North America (ENA) as a whole and for the Atlantic (ATL) and Mississippi (MISS) flyways separately. We then used linear models and Akaike’s Information Criterion with small-sample size correction (AICc) model selection to test whether species traits could explain variation in range shifts or flyway discrepancies. Across ENA, most species showed northward latitudinal range shifts, but some showed no latitudinal shift while others shifted southwards. Amongst ATL and MISS, we documented both within- and between-species differences in the rate and direction of latitudinal shifts, complicating the results from across ENA. No single trait emerged as a dominant driver of range shift differences at the ENA and flyway scales. Migration strategy interacted with insectivory to explain variation at the largest spatial scale (ENA), whereas frugivory and mean winter latitude explained much of the variation in ATL and MISS, respectively. Exploring heterogeneity in range shifts within and between species, and in the associations between range shifts and life history traits, will help us better understand the mechanisms that mediate differing responses to environmental change and predict which species will be better able to adapt to those changes.

Migratory patterns of mallards in eastern North America as revealed from band‐recovery data

AbstractMallard (Anas platyrhynchos) distributions have changed in North America over the last century because of altered habitat and the direct augmentation of eastern populations with captive‐bred game‐farm mallards in the early twentieth century. Geographical overlap between wild and game‐farm individuals has resulted in interbreeding, with North American mallard populations now ranging from largely wild to more feral and feral x wild hybrids. How changing genetic integrity of North America's mallards translates behaviorally remains unknown. We analyzed band‐recovery data from 1949–2019 to estimate emigration rates and geographic distributions of mallards to understand whether the admixed genetic heritage of mallards in North America's Mississippi and Atlantic flyways resulted in variable autumn distributions. We included American black ducks (Anas rubripes) as a flyway migratory comparative, and analyzed datasets partitioned by flyway and major international space (i.e., Canada vs. United States). We present results that correspond to the hypothesis that western mallard populations of the 1950s expanded eastward and were the precursor populations of mallards in the Canadian provinces of the Atlantic Flyway, while mallards of the Atlantic Flyway in the United States showed substantially differing patterns. Specifically, we estimate that since 1990, approximately 23% of banded mallards on the United States side of the Atlantic Flyway are annually recovered in the Mississippi Flyway as compared to about 5% of those banded in Canadian provinces of the Atlantic Flyway. Given that mallards from the United States side of the Atlantic Flyway are considered a feral × wild hybrid swarm, annual westward emigration of 23% of these mallards is concordant with increasing prevalence of game‐farm mallard molecular variation detected in the Great Lakes and mid‐continent mallard populations. Our results provide insight into potential means for the movement of game‐farm molecular variation from the Atlantic into the Mississippi Flyway, and suggest that the effect of these mallards on the genetic integrity and future adaptive capacity of mallard populations in the Mississippi Flyway requires attention and consideration in future management decisions.

Guest Editors' Introduction: Protected Areas of the American Southeast

Guest Editors' Introduction:Protected Areas of the American Southeast Joe Weber and John A. Kupfer Protected areas (PAs) in the United States are lands and waters that are: 1) dedicated to the preservation of biological diversity and other natural, recreational, and cultural uses, and 2) managed for these purposes through legal or other effective means (U.S. Geological Survey Gap Analysis Project 2022). Such areas are overseen by a suite of federal, state, tribal, and local authorities and encompass everything from national and state parks and forests to wildlife refuges, tribal lands, military bases, regional land and water management areas, county and local parks, and privately owned lands protected through conservation easements. Because of the diverse nature of PAs and the organizations charged with managing them, their goals, missions, and permissible activities are highly varied, ranging from conservation of biodiversity, recreation, farming and forestry, protection of water supply and quality, hazard prevention, scenic protection, and much more. Protected areas are also places that connect Americans to their history and heritage and that provide sources of inspiration and personal renewal (Kupfer et al. 2021). The southeastern United States contains an array of endemic species and unique ecosystems that occupy habitats from the highest peaks of the Appalachian Mountains to marine environments along the Atlantic and Gulf coasts, making it one of the world's thirty-six biodiversity hotspots (Noss et al. 2015). The region is also home to a range of cultures, fascinating urban and rural landscapes, scenes of conflict, and artistic triumphs. The rich biological, cultural, social, and historical heritage of the region is reflected in the important role that it has played in the genesis, growth, and diversification of PAs nationally. The first national wildlife refuge was created in Florida in 1903 to protect brown pelicans and other birds from slaughter by market and plume hunters; and national wildlife refuges throughout the region continue to provide habitat for threatened and endangered species such as the American crocodile, gopher tortoise, and Mississippi sandhill crane as well as critical stopover points along the Atlantic and Mississippi flyways. Following passage of the Weeks Act in 1911, Pisgah National Forest in western North Carolina was the first national forest created from private lands when it was established in 1916. It is now considered to be part of the Cradle of American Forestry. Everglades National Park was the first National Park System unit created primarily to protect an [End Page 6] ecosystem, and it remains the largest tropical wilderness in the US and the largest wilderness of any kind east of the Mississippi River (Lodge 2016). Military installations protect numerous imperiled species and ecosystems (Stein et al. 2008) and provide valuable examples of approaches for balancing conflicting uses as part of ecosystem-based management (Christensen et al. 2021). And, while the majority of US protected lands are in the American West, more vulnerable species are found in the Southeast, emphasizing the importance of protecting private lands in the region (Jenkins et al. 2015). The Nature Conservancy's first large protection project was on the Pascagoula River in Mississippi in the 1970s (Schueler 2002), and more than 1 million hectares throughout the region are protected under conservation easements (National Conservation Easement Database 2022). These examples, and numerous others not mentioned here, underscore the important role of PAs in the protection and management of biodiversity in the Southeast. The Southeast is also home to the first federal attempts at protecting cultural and historical sites. These efforts began in the 1890s when five Civil War battlefields (Chickamauga and Chattanooga, Shiloh, Vicksburg, Antietam, and Gettysburg) were purchased by the U.S. Army (using the powers of eminent domain, when needed) and preserved as national military parks (Lee 1973, Smith 2008). The Army restored these battlefields to their wartime appearance, established roads, put up interpretive and commemorative markers, and hired staff to protect and maintain the parks. These sites were joined by many others in the Southeast before eventually being transferred to the National Park Service (NPS) in 1933. The transfer of these sites was part of a larger effort by the NPS to expand into units focused more on history and recreation and represented a geographic strategy to...

Migration patterns and habitat use by molt migrant temperate‐breeding Canada geese in James Bay, Canada

Numbers of temperate‐breeding Atlantic and Mississippi Flyway Canada geese have greatly increased since the 1980s. Consequently, numbers of yearlings, sub‐adults and failed breeders undertaking pre‐molt migration to northern latitudes has also increased, potentially providing additional hunting opportunities for Cree hunters living near James Bay, Canada. We described movement patterns and habitat use of molt migrant Canada geese Brenta canadensis maxima along the east coast of James Bay based on nine geese fitted with GSM–GPS devices during 11 northward and eight southward migrations between 2015 and 2019. Geese staged for 2.8 ± 0.6 days (mean ± standard error of the mean) at 3.2 ± 0.6 staging sites (mostly tidal flats and salt marshes) from the first week of June in spring and 3.8 ± 1.8 days at 2.0 ± 0.5 staging sites (mostly inland freshwater wetlands, peatlands and tidal flats) from the first week of September when returning south. Shallow and deep water habitats were used as resting sites during both migrations. In spring, molt migrants were mostly harvested in June well after the migration of sub‐arctic breeding geese whereas in autumn, both subspecies were harvested in September. Molt migrant temperate‐breeding geese can increase harvest opportunities and represent supplementary wildlife food for Cree communities. However, the current number of molt migrant geese harvested by Cree hunters is not sufficient to significantly impact populations of temperate‐breeding geese.

Low levels of hybridization between domestic and wild Mallards wintering in the lower Mississippi Flyway

Abstract The Mallard (Anas platyrhynchos) duck is a ubiquitous and socio-economically important game bird in North America. Despite their generally abundant midcontinent population, Mallards in eastern North America are declining, which may be partially explained by extensive hybridization with human-released domestically derived game-farm Mallards. We investigated the genetic composition of Mallards in the middle and lower Mississippi flyway, key wintering regions for the species. We found that nearly 30% of wild Mallards carried mitochondrial (mtDNA) haplotypes derived from domestic Mallards present in North America, indicating that the individuals had female game-farm Mallard lineage in their past; however, nuclear results identified only 4% of the same sample set as putative hybrids. Recovering 30% of samples with Old World (OW) A mtDNA haplotypes is concordant with general trends across the Mississippi flyway and this percentage was stable across Mallards we sampled a decade apart. The capture and perpetuation of OW A mtDNA haplotypes are likely due to female breeding structure, whereas reversal of the nuclear signal back to wild ancestry is due to sequential backcrossing and lower and/or declining admixture with game-farm Mallards. Future studies of wild ancestry of Mississippi flyway Mallards will benefit from coupling molecular and spatial technology across flyways, seasons, and years to search for potential transitions of Mallard populations with different genetic ancestry, and whether the genetic ancestry is somehow linked to an individual’s natal and subsequent breeding location.

Resource Use Overlap by Sympatric Wintering American Black Ducks and Mallards in Tennessee

Abstract American black ducks Anas rubripes are declining in traditionally important wintering areas in the south-central Mississippi flyway. Understanding resource exploitation by black ducks and morphologically similar and co-existing mallards Anas platyrhynchos during winter may provide insight into competitive interactions that could exacerbate these declines. We radiomarked female black ducks and mallards at the Tennessee National Wildlife Refuge, Tennessee, USA, during winter 2011–2012. We hypothesized that resource partitioning may occur to avoid or lessen interspecific competition between the two species and examined this possibility in the context of home range overlap, resource selection and proportional resource use, niche breadth, and inter- and intraspecific resource overlap. Black duck and mallard home ranges were similar in area, with black duck individual home ranges ranging from 15 to 77 km2 and mallards from 21 to 72 km2 in size; 93% of the total area used by each species overlapped. Black ducks selected emergent wetlands 1.2× more than mallards, and mallards selected cultivated lands 2× more than black ducks. However, there were only minor differences between species in their proportional use of landcover types, and there were no temporal differences in resource selection at diurnal or seasonal scales. Additionally, while black ducks and mallards had moderate and small niche breadths (niche breadth = 0.47 and 0.34, respectively), the two species had a substantial degree of inter- and intraspecific resource overlap. Our results indicate these species do not competitively exclude each other spatiotemporally. Further research is needed to understand fine-scale interactions between these species and other factors that may be affecting black duck declines in the south-central Mississippi flyway, such as effects occurring in the breeding grounds or the potential influences of climate on northern shifts in duck distribution.

Citizen science reveals waterfowl responses to extreme winter weather.

Global climate change is increasing the frequency and severity of extreme climatic events (ECEs) which may be especially detrimental during late‐winter when many species are surviving on scarce resources. However, monitoring animal populations relative to ECEs is logistically challenging. Crowd‐sourced datasets may provide opportunity to monitor species' responses to short‐term chance phenomena such as ECEs. We used 14 years of eBird—a global citizen science initiative—to examine distribution changes for seven wintering waterfowl species across North America in response to recent extreme winter polar vortex disruptions. To validate inferences from eBird, we compared eBird distribution changes against locational data from 362 GPS‐tagged Mallards (Anas platyrhynchos) in the Mississippi Flyway. Distributional shifts between eBird and GPS‐tagged Mallards were similar following an ECE in February 2021. In general, the ECE affected continental waterfowl population distributions; however, responses were variable across species and flyways. Waterfowl distributions tended to stay near wintering latitudes or moved north at lesser distances compared with non‐ECE years, suggesting preparedness for spring migration was a stronger “pull” than extreme weather was a “push” pressure. Surprisingly, larger‐bodied waterfowl with grubbing foraging strategies (i.e., geese) delayed their northward range shift during ECE years, whereas smaller‐bodied ducks were less affected. Lastly, wetland obligate species shifted southward during ECE years. Collectively, these results suggest specialized foraging strategies likely related to resource limitations, but not body size, necessitate movement from extreme late‐winter weather in waterfowl. Our results demonstrate eBird's potential to monitor population‐level effects of weather events, especially severe ECEs. eBird and other crowd‐sourced datasets can be valuable to identify species which are adaptable or vulnerable to ECEs and thus, begin to inform conservation policy and management to combat negative effects of global climate change.

Food Selection by Spring-Migrating Green-Winged Teal

AbstractThe Mississippi Flyway supports millions of waterfowl during spring migration as individuals replenish vital nutrients en route to breeding locations. Green-winged teal Anas crecca consume natural plant and animal foods in shallow wetlands during autumn and winter, but little information is available to describe food use and selection during spring migration. We experimentally collected green-winged teal and quantified food use and availability to determine selection in the Illinois River Valley during February–April 2016–2018. We removed, dried, and weighed (±0.1 mg) food items by taxa from the upper digestive tract (proventriculus and esophagus) of birds and core samples for comparison. Additionally, we evaluated retention of common diet items between small (#60; 250 μm) and medium (#35; 500 μm) sieves and the effect of processing sieve size on selection coefficients. Seeds of moist-soil vegetation occurred in all green-winged teal diets, while invertebrates and vegetation material occurred in 67.4% and 25.8% of diets, respectively. Green-winged teal consumed 85.8% (CI95 = 81.2–90.3%) plant material and 14.2% (CI95 = 9.6–18.7%) invertebrates based on aggregate dry biomass. We failed to find support for selection of either plant or animal foods in general, but green-winged teal selected Cyperus spp., Ammannia spp., Leptochloa spp., and Potamogeton spp. and avoided Amaranthus spp., Ipomoea spp., Echinochloa spp., and Oligochaeta individual taxa. We found no support for a difference in selection ratios between sexes, but selection ratios differed among years and wetland connectivity regimes with changes in food availability. Sieve size had minimal impact on rank and selection intensity of most food items, but only small sieves captured Ammannia spp., which was an important diet item. We found no evidence that green-winged teal selected invertebrates in our midlatitude migration study area, as has been speculated for dabbling ducks in general during spring migration (i.e., spring diet-shift hypothesis). We encourage managers to provide shallowly flooded wetlands with desirable plant taxa (e.g., Cyperus spp., Ammannia spp., Leptochloa spp.) for green-winged teal by maintaining actively managed moist-soil wetlands that are made available during spring migration.

Effects of weather variation on waterfowl migration: Lessons from a continental-scale generalizable avian movement and energetics model.

We developed a continental energetics‐based model of daily mallard (Anas platyrhynchos) movement during the non‐breeding period (September to May) to predict year‐specific migration and overwinter occurrence. The model approximates movements and stopovers as functions of metabolism and weather, in terms of temperature and frozen precipitation (i.e., snow). The model is a Markov process operating at the population level and is parameterized through a review of literature. We applied the model to 62 years of daily weather data for the non‐breeding period. The average proportion of available habitat decreased as weather severity increased, with mortality decreasing as the proportion of available habitat increased. The most commonly used locations during the course of the non‐breeding period were generally consistent across years, with the most inter‐annual variation present in the overwintering area. Our model revealed that the distribution of mallards on the landscape changed more dramatically when the variation in daily available habitat was greater. The main routes for avian migration in North America were predicted by our simulations: the Atlantic, Mississippi, Central, and Pacific flyways. Our model predicted an average of 77.4% survivorship for the non‐breeding period across all years (range = 76.4%–78.4%), with lowest survivorship during autumn (90.5 ± 1.4%), intermediate survivorship in winter (91.8 ± 0.7%), and greatest survivorship in spring (93.6 ± 1.1%). We provide the parameters necessary for exploration within and among other taxa to leverage the generalizability of this migration model to a broader expanse of bird species, and across a range of climate change and land use/land cover change scenarios.

Environmental drivers of autumn migration departure decisions in midcontinental mallards

BackgroundThe timing of autumn migration in ducks is influenced by a range of environmental conditions that may elicit individual experiences and responses from individual birds, yet most studies have investigated relationships at the population level. We used data from individual satellite-tracked mallards (Anas platyrhynchos) to model the timing and environmental drivers of autumn migration movements at a continental scale.MethodsWe combined two sets of location records (2004–2007 and 2010–2011) from satellite-tracked mallards during autumn migration in the Mississippi Flyway, and identified records that indicated the start of long-range (≥ 30 km) southward movements during the migration period. We modeled selection of departure date by individual mallards using a discrete choice model accounting for heterogeneity in individual preferences. We developed candidate models to predict the departure date, conditional on daily mean environmental covariates (i.e. temperature, snow and ice cover, wind conditions, precipitation, cloud cover, and pressure) at a 32 × 32 km resolution. We ranked model performance with the Bayesian Information Criterion.ResultsDeparture was best predicted (60% accuracy) by a “winter conditions” model containing temperature, and depth and duration of snow cover. Models conditional on wind speed, precipitation, pressure variation, and cloud cover received lower support. Number of days of snow cover, recently experienced snow cover (snow days) and current snow cover had the strongest positive effect on departure likelihood, followed by number of experienced days of freezing temperature (frost days) and current low temperature. Distributions of dominant drivers and of correct vs incorrect prediction along the movement tracks indicate that these responses applied throughout the latitudinal range of migration. Among recorded departures, most were driven by snow days (65%) followed by current temperature (30%).ConclusionsOur results indicate that among the tested environmental parameters, the dominant environmental driver of departure decision in autumn-migrating mallards was the onset of snow conditions, and secondarily the onset of temperatures close to, or below, the freezing point. Mallards are likely to relocate southwards quickly when faced with snowy conditions, and could use declining temperatures as a more graduated early cue for departure. Our findings provide further insights into the functional response of mallards to weather factors during the migration period that ultimately determine seasonal distributions.

Variation in the Diet of Ducks During Spring Migration

ABSTRACTBecause 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.

Half‐Century Winter Duck Abundance and Temperature Trends in the Mississippi and Atlantic Flyways

ABSTRACTIncreasing concerns exist about possible decreased wintering duck abundance and hunting opportunities in the southern regions of the Atlantic and Mississippi flyways of North America. Researchers suggest these decreased abundances of ducks may be related to winter warming and related climatic phenomena. Accordingly, we tested predictions that duck abundance was increasing more at northern than southern latitudes, and that trends were related to average winter temperatures (Dec–Jan). We tested predictions using National Audubon Society Christmas Bird Count (CBC) data collected during December 1969 through January 2019 from 31 states in the United States and 6 Canadian provinces that comprise the Atlantic and Mississippi flyways for 16 species of dabbling and diving ducks (Anatinae). We found support for the prediction that CBC trends in duck abundance vary with latitude, and mean winter temperature explained nearly half the variation in CBC trends for 12 of 16 species. For some species, trends were negative in warmer regions and positive in colder regions. For others, trends were stable or slightly positive in warmer regions but more positive in colder regions. These results provide empirical evidence supporting climate‐influenced winter range changes by important game duck species and suggest challenges and opportunities for waterfowl population, habitat, and hunting management in North America and the northern hemisphere. © 2021 The Wildlife Society.

Migration phenology and patterns of American woodcock in central North America derived using satellite telemetry

American woodcock Scolopax minor (hereafter woodcock) migration ecology is poorly understood, but has implications for population ecology and management, especially related to harvest. To describe woodcock migration patterns and phenology, we captured and equipped 73 woodcock with satellite tracking devices in the Central Management Region (analogous to the Mississippi Flyway) of North America and documented migration paths of 60 individual woodcock and 87 autumn or spring woodcock migrations during 2014–2016. Woodcock migration at the scale of the Central Management Region was more synchronous in spring than in autumn, but unlike most other migratory birds, average duration of autumn migration (31 days) was shorter than duration of spring migration (53 days). This difference in migration duration resulted from woodcock making more close-together migratory stopovers during spring migration, not because woodcock had individual stopovers of longer duration. During autumn migration, the number of days, the number of stopovers, migration end date and net migration displacement were negatively related to initiation date and rate of migration, and the number of stopovers and the net migration displacement were negatively related with migration end date. Spring migration duration, end date, the number of stopovers and net migration displacement were negatively related to migration rate and initiation date was positively related to migration rate, suggesting that woodcock that initiated spring migration later had faster migration rates. Juvenile female woodcock began spring migration later than adult female woodcock. Our results provide a basis for comparing current harvest seasons with presence of migrating woodcock during autumn and provide insight into differential harvest of migratory versus local woodcock on breeding areas.