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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.

The equilibrium theorem provided a fundamental framework for understanding species’ distributions and movement in fragmented ecosystems. Wetland-dependent avian species are model organisms to test insular predictions within protected area networks because their mobility allows surveillance of isolated patches without landscape barriers. We hypothesized size and isolation would influence functional connectivity of sanctuaries by GPS-marked wintering mallards ( Anas platyrhynchos ) within a mesocosm protected sanctuary area network. We evaluated functional connectivity and sanctuary use, measured by movements between sanctuaries, using a multistate modeling framework. Proximity drove connectivity, underscoring that patch isolation—not size—influenced connectivity, even for an avian species with no ascertainable landscape resistance or barriers. We also found that sanctuary use increased overwintering survival by reducing harvest mortality. Our test of equilibrium theory predictions demonstrated that isolation of protected sanctuary areas supersedes their size in determining functional connectivity for mallards and access to these areas may have direct fitness consequences. Our findings could refine land acquisition, restoration, and management practices with equal or greater emphasis on adjacency in protected area network design, especially for wetland-dependent migratory gamebirds.

Testing of ducks in Tennessee, United States, before introduction of highly pathogenic influenza A(H5N1) virus demonstrated a high prevalence of antibodies to influenza A virus but very low prevalence of antibodies to H5 (25%) or H5 and N1 (13%) subtypes. Antibody prevalence increased after H5N1 introduction.

Human activities in natural areas can impose both lethal and non‐lethal impacts on animals. Furthermore, anthropogenic disturbance is analogous to predation risk and can cause animals to adjust their behaviors to avoid humans. Quantifying whether disturbance‐induced behavioral shifts affect individual fitness or population dynamics is needed to guide science‐based conservation and management decisions. We experimentally disturbed GPS‐marked mallards (Anas platyrhynchos) on sanctuaries weekly to evaluate the effects of brief pulses (1 h) of non‐lethal anthropogenic disturbance on individual survival. We used Cox proportional hazard models to examine how single and cumulative disturbance affected survival and tested whether body mass or hunting season mediated the effects of disturbance. One hundred and eighty‐eight mallards were disturbed ≥1 time resulting in 629 disturbance encounters. Only 3 individuals died immediately following disturbance, representing <0.5% of encounters. Collectively, we found no effect of disturbance on daily survival, and our cumulative disturbance model showed undisturbed mallards had lower survival than disturbed mallards. Standardized body mass or hunting season did not mediate the effect of disturbance on survival. Together, we concluded there was no effect of our brief experimental disturbance treatments on mallard survival. Instead, diurnal sanctuary use and individual characteristics, including age, sex, and standardized body mass, affected survival. Diurnal sanctuary use was positively related to survival, and for every 20% increase in diurnal sanctuary use, the risk of mortality decreased by 15%. Additionally, female mallards were 2.7 times more likely to die compared to males, and juveniles had a 53% greater risk of mortality than adults. Lastly, for every 100 g heavier than average mallards were, we found a 23% lower risk of mortality during our study. If a primary goal of waterfowl sanctuary is including non‐consumptive recreational use, our results suggest controlled access (e.g., ~1 h/week) may have minimal effects on survival and be consistent with multi‐use objectives on public lands with waterfowl sanctuaries. If additional recreational access to support multiple public uses is a goal on public lands managed as sanctuaries, we recommend future work identify disturbance thresholds at which point survival or other fitness metrics are impacted by disturbance related to public uses of protected areas.

Animal movement influences local transmission and geographic spread of pathogens. Waterfowl are known reservoirs of pathogens, including H5 goose/Guangdong lineage (H5 GsGd) highly pathogenic avian influenza (HPAI). This HPAI virus lineage causes high rates of morbidity and mortality in domestic poultry and many wild bird species. Mallards (Anas platyrhynchos) are a generalist waterfowl species whose habitat largely overlaps with many other waterfowl and are considered effective spillover vectors of HPAI. To investigate the potential contribution of waterfowl to HPAI spillover, we used mallards as a proxy and measured the spatiotemporal overlap of 183 GPS‐tagged mallards during 2021–2022 with respect to confirmed wild bird spillover events in United States (U.S.) poultry farms. Additionally, we estimated the probability of HPAI spillover events as a function of mallard overlap and poultry farm type. We found infrequent overlap instances between mallards and poultry farms; however, several of these overlap instances lasted > 5 days and up to 19 days. Population‐level overlap with poultry farms was greatest during pre‐breeding migration, followed by the breeding season. The probability of HPAI spillover was predicted to be greatest for commercial turkey farms, followed by backyard poultry farms. Importantly, farms overlapped by mallards were more than twice as likely to experience a spillover (i.e., increased risk probability), even in the absence of known mallard infection status at the time of overlap. These findings suggest that mallards (and/or other waterfowl) may be important contributors to HPAI spillover into poultry farms and that additional biosecurity measures may be needed. Because few instances of overlap occurred between mallards and farms with reported spillover events, tagged mallards are likely a proxy for other untagged waterfowl. Further studies of wild waterfowl interactions with poultry farms could improve understanding of how landscape characteristics influence spatial overlap, potentially informing which premises may require enhanced biosecurity measures. GPS‐tagged mallards served as a proxy for wild waterfowl spillover of highly pathogenic avian influenza at domestic poultry farms. Farms overlapped by mallards in space and time were more than twice as likely to experience a spillover event.

Introgressive hybridization, the interbreeding and gene flow between different species, has become increasingly common in the Anthropocene, where human‐induced ecological changes and the introduction of captively reared individuals are increasing secondary contact among closely related species, leading to gene flow between wild and domesticated lineages. As a result, domesticated‐wild hybridization may potentially affect individual fitness, leading to maladaptive effects such as shifts in behavior or life‐history decisions (e.g., migration patterns), which could influence population demographics. In North America, the release of captive‐reared game‐farm mallards (Anas platyrhynchos) for hunting has led to extensive hybridization with wild mallards, altering the genetic structure in the Atlantic and Mississippi flyways. We aimed to investigate differences in spring migratory behavior among 296 GPS‐tagged mallards captured during winter in Tennessee and Arkansas with varying levels of hybridization. Despite relatively low levels of genetic introgression of game‐farm genes, mallards with higher percentages of game‐farm ancestry exhibited later departure and arrival times, shorter migration distances, and a tendency to establish residency at lower latitudes. Specifically, for every 10% increase in game‐farm genetics, mallards departed 17.7% later, arrived 22.1% later, settled 3.3% farther south, and traveled 7.1% shorter distances during migration. These findings suggest that genetic introgression from game‐farm mallards influences migratory behavior, potentially reducing fitness, and contributing to population declines in wild mallards. Our study presents a need for understanding how domestic hybridization effects fitness and behavioral change of other species. Domesticated‐wild hybridization between game‐farm and wild mallards (Anas platyrhynchos) may impact migratory behavior and fitness. In this study, we analyzed spring migration data from 296 GPS‐tagged mallards in Tennessee and Arkansas, finding that higher levels of game‐farm ancestry were associated with delayed departure and arrival times, shorter migration distances, and settlement at lower latitudes. Our study presents a need for understanding how game‐farm mallards are influencing breeding activities and understanding regional effects of hybridization.

Background Migration in birds results from a complex interplay of internal and environmental cues that shift across seasons. A push–pull framework conceptualizes migration as driven by external “push” cues, such as deteriorating weather, and internal “pull” cues associated with photoperiod and reproductive readiness. Understanding how these cues interact seasonally can inform predictions about migratory behavior under changing climatic conditions. Methods We applied the push–pull framework to assess drivers of seasonal migration in mallards ( Anas platyrhynchos ), a behaviorally plastic waterfowl species. We analyzed GPS data from 414 individuals tracked across the Mississippi Flyway from 2019 to 2024. Monthly migration direction and distance were modeled as functions of minimum temperature, wind direction, barometric pressure change, and photoperiod. We examined how cue influence varied between autumn and spring migration periods. Results By December 31, ~92% of southward migrations had occurred, with ~50% completed by mid-November. Autumn migration was primarily influenced by environmental push cues—declining temperatures, favorable wind direction, and falling barometric pressure all increased the likelihood and distance of migration. Migration distances peaked in November and December, when these push conditions were strongest. In contrast, spring migration was driven more by internal pull cues. Northward movements initiated in January and intensified through April, with photoperiod overriding weather as the primary driver. Weather still affected migration distances, e.g. warmer minimum temperatures in February increased distances by 62%, while strong north winds in March reduced movement by up to 213%. Barometric pressure had opposing effects by season: falling pressure promoted movement in autumn but inconsistently influenced spring migration. Conclusions Our findings reveal a seasonal shift in the relative influence of environmental and internal cues on mallard migration. Weather exerts stronger influence during autumn, whereas photoperiod dominates in spring. These results highlight the utility of a push–pull framework for understanding migratory behavior and suggest that climate change may disproportionately disrupt the reliability of migration cues across seasons.

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.

The Florida mottled duck (Anas fulvigula fulvigula) is threatened by introgression through hybridization with feral mallards (A. platyrhynchos). An essential component in managing this threat is the ability to accurately distinguish mottled ducks from mallards and hybrids in the wild. We provide a genetically cross-validated phenotype key that accurately identifies mottled ducks. We collected data on structural and plumage traits from museum specimens of Florida, USA, mottled ducks and mallards to identify morphological traits useful in this process. We performed extensive comparisons and discriminant function analysis to identify traits informative in distinguishing the 2 species. We used these traits to preliminarily assign 168 contemporary birds as putative mottled duck, mallard, or hybrid. We collected tissue samples from each contemporary specimen and amplified and genotyped associated DNA. We used microsatellite markers to determine posterior probability species assignments for the 168 specimens. We then performed recursive partitioning of phenotypic traits and posterior genotype assignments to create identification keys based on the most informative traits separating mottled ducks from mallards and hybrids. Finally, we cross-validated the keys by comparing assignments made using the key to those from genotyping for 339 wild ducks. The keys were >90% accurate, which suggests that their adoption will increase the ability of managers to address the threat of hybridization by mallards by allowing mottled ducks to be distinguished from other ducks in Florida. Our research provides a methodology to develop genetically cross-validated identification keys for other species threatened by genetic introgression.