Why Are Numbers of Mallards (<i>Anas platyrhynchos</i>) Declining In the Northeastern United States? The Possible Role of Reduction In Winter Feeding Sites

Heusmann, H. W.

doi:10.1676/16-044.1

Cited by 4 publications

(4 citation statements)

References 16 publications

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“…The causes of population decline in black ducks and the eastern North American mallard population (the latter observable only over the past 20 years) are debated (Heusmann, ; USFWS, ). We predict that the significant input of maladaptive genes from game‐farm mallards over the last century is one important cause.…”

Section: Discussionmentioning

confidence: 99%

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Assessing changes in genomic divergence following a century of human‐mediated secondary contact among wild and captive‐bred ducks

et al. 2020

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Along with manipulating habitat, the direct release of domesticated individuals into the wild is a practice used worldwide to augment wildlife populations. We test between possible outcomes of human‐mediated secondary contact using genomic techniques at both historical and contemporary timescales for two iconic duck species. First, we sequence several thousand ddRAD‐seq loci for contemporary mallards (Anas platyrhynchos) throughout North America and two domestic mallard types (i.e., known game‐farm mallards and feral Khaki Campbell's). We show that North American mallards may well be becoming a hybrid swarm due to interbreeding with domesticated game‐farm mallards released for hunting. Next, to attain a historical perspective, we applied a bait‐capture array targeting thousands of loci in century‐old (1842–1915) and contemporary (2009–2010) mallard and American black duck (Anas rubripes) specimens. We conclude that American black ducks and mallards have always been closely related, with a divergence time of ~600,000 years before present, and likely evolved through prolonged isolation followed by limited bouts of gene flow (i.e., secondary contact). They continue to maintain genetic separation, a finding that overturns decades of prior research and speculation suggesting the genetic extinction of the American black duck due to contemporary interbreeding with mallards. Thus, despite having high rates of hybridization, actual gene flow is limited between mallards and American black ducks. Conversely, our historical and contemporary data confirm that the intensive stocking of game‐farm mallards during the last ~100 years has fundamentally changed the genetic integrity of North America's wild mallard population, especially in the east. It thus becomes of great interest to ask whether the iconic North American mallard is declining in the wild due to introgression of maladaptive traits from domesticated forms. Moreover, we hypothesize that differential gene flow from domestic game‐farm mallards into the wild mallard population may explain the overall temporal increase in differentiation between wild black ducks and mallards, as well as the uncoupling of genetic diversity and effective population size estimates across time in our results. Finally, our findings highlight how genomic methods can recover complex population histories by capturing DNA preserved in traditional museum specimens.

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Section: Discussionmentioning

confidence: 99%

“…The causes of population decline in black ducks and the eastern North American mallard population (the latter observable only over the past 20 years) are debated (Heusmann, 2017;USFWS, 2013).…”

Section: F I G U R Ementioning

confidence: 99%

Assessing changes in genomic divergence following a century of human‐mediated secondary contact among wild and captive‐bred ducks

et al. 2020

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“…Hunting regulations in eastern Canada are relatively stable and for purposes of this research we assumed harvests of the five species would be comparable to those observed since 1997. All regulatory options considered in this study for the Atlantic Flyway have a reduced bag limit of two mallards to provide additional protection for the declining Atlantic Flyway population (Heusmann, ; Sauer et al., ). The wood duck bag limit in the 60/6 option was changed from two birds to three in 2008.…”

Section: Methodsmentioning

confidence: 99%

Multi‐species duck harvesting using dynamic programming and multi‐criteria decision analysis

Johnson

Zimmerman

Huang

et al. 2019

Journal of Applied Ecology

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1. Multiple species are often exposed to a common hunting season, but harvest and population objectives may not be fully achieved if harvest potential varies among species and/or species abundances are not correlated through time. Our goal was to develop an approach for setting a common hunting season that would recognize heterogeneity in species productivity and would select annual hunting seasons conditioned on the status of individual species.2. We first used stochastic dynamic programming to generate optimal, state-dependent harvest strategies for 18 candidate regulatory scenarios. We simulated the performance of these strategies, and then used multi-criteria decision analysis to identify preferred regulatory scenarios for duck hunting seasons in the Atlantic Flyway of the U.S.3. Generally, estimates of annual population size were not correlated among species.Mallards had the highest estimated intrinsic rate of growth, green-winged teal, wood ducks, and ring-necked ducks had intermediate values, and goldeneyes were the least productive. Estimated carrying capacity was highest for mallards and lowest for green-winged teal. 4. Managers had greatest interest in maximizing season length (33%) and aggregate duck abundance (28%), and less interest in maximizing aggregate harvest (19%) and the number of years between a change in hunting season regulations (19%).Several regulatory scenarios provided acceptable trade-offs among these objectives. Synthesis and applications.Separate hunting seasons for various species of game may be untenable, either due to the added cost and regulatory complexity, or because selective harvesting of stocks may be difficult due to problems in species identification. Rather than averaging species-specific productivities, or basing hunting seasons on the least (or most) productive species, we describe an approach in which productivity and annual population status are considered 1448 | Journal of Applied Ecology JOHNSON et al.

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“…Mallards can nest successfully in urban parks and residential neighborhoods (Figley and VanDruff 1982, Master and Oplinger 1984, Engel et al 1988), including in the urbanized landscapes of Connecticut, USA (Dykstra 2023). Mallards tolerate humans (Figley and VanDruff 1982, Traut and Hostetler 2003) and benefit from artificial feeding in parks, which allows them to overwinter in great densities (Heusmann 1988), but females often leave parks to nest and rear broods in adjacent undeveloped, natural areas (Heusmann 1981). In urbanized landscapes, ducklings risk mortality from disturbance by humans or pets, vehicular traffic, human‐made obstacles (e.g., storm sewers, fences), and insufficient cover to protect ducklings from predators (Figley and VanDruff 1982, Seymour and Jackson 1996).…”

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confidence: 99%

Mallard brood movements and survival in an urbanized landscape

Dykstra,

Huang,

Rittenhouse

2024

J Wildl Manag

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When selecting a nest site, mallards (Anas platyrhynchos) balance differing habitat requirements for the nesting and brood‐rearing periods, such that the juxtaposition of these habitats in the landscape may influence the female's reproductive strategy and reproductive success. Mallard populations in the northeastern United States have declined since the mid‐1990s, and increasing urban development in this region may pose risks to broods and cause high duckling mortality. We assessed mallard brood and duckling survival in the urbanized landscapes of Connecticut, USA, and evaluated whether differences in brood movements, home ranges, and habitat use in urbanized areas influence brood survival. We monitored 32 mallard broods from females with global positioning system (GPS) transmitters in Connecticut in 2021 and 2022. Apparent brood survival to 30 days (0.48, n = 29 broods) was comparable to previous estimates in the Northeast (range = 0.21–0.72), but individual duckling survival (0.18, n = 257 ducklings) was lower than many previous estimates for this region (range = 0.14–0.44), suggesting this parameter warrants continued evaluation because it may be contributing to population declines in Connecticut and the greater Northeast region. Mallard females demonstrated different reproductive strategies and seemed to prioritize either high‐quality nesting habitat or proximity to high‐quality brood‐rearing habitat. High‐quality nesting habitat is not necessarily near high‐quality brood‐rearing habitat, and 61% (17/28) of females moved their ducklings an average of 1.1 ± 0.9 km (SD) shortly after hatch to a brood‐rearing site, often traveling along small streams. A similar proportion of successful (9/12) and failed (7/13) broods moved. We provide evidence of limited availability of brood‐rearing habitat, as females moved long distances to brood‐rearing wetlands and only 1 brood made additional inter‐wetland moves. Management actions that create or modify nesting and brood‐rearing habitat should consider connectivity between these sites; females may choose to nest away from wetlands to minimize exposure to predators but may depend on small streams for travel to brood‐rearing wetlands.

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Why Are Numbers of Mallards (Anas platyrhynchos) Declining In the Northeastern United States? The Possible Role of Reduction In Winter Feeding Sites

Cited by 4 publications

References 16 publications

Assessing changes in genomic divergence following a century of human‐mediated secondary contact among wild and captive‐bred ducks

Assessing changes in genomic divergence following a century of human‐mediated secondary contact among wild and captive‐bred ducks

Multi‐species duck harvesting using dynamic programming and multi‐criteria decision analysis

Mallard brood movements and survival in an urbanized landscape

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