Mallard (Anas platyrhynchos) abundance in the Great Lakes states declined by 30% from 2000 to 2023 based on spring aerial surveys in Michigan, Minnesota, and Wisconsin. Concern among management agencies and uncertainty in the factors contributing to Great Lakes mallard decline led to a regional partnership which initiated this research project. The research objectives were to estimate Great Lakes mallard demographic parameters, determine which parameters had driven declines in abundance, and reduce uncertainty about the ecological and anthropogenic factors affecting movement and population dynamics. We captured, collected genetic and feather samples from, and marked 592 female mallards with GPS-GSM transmitters in Michigan, Wisconsin, Ohio, Indiana, and Illinois, USA from 2021–2023. We also used 32 years of banding, band recovery, and aerial survey data collected from mallards in Michigan and Wisconsin during 1991–2022 to develop an Integrated Population Model (IPM). Genetic ancestry analysis of GPS-marked female mallards via ddRAD sequencing revealed 44% were wild mallards and 56% were wild x domestic game-farm mallard hybrids. Hybrid mallards had shorter daily movement distances, were less likely to engage in autumn migration, and had higher use and selection of urban developed land cover than did wild mallards. Survival of female GPS-marked mallards was positively related to the proportion of locations in urban developed land cover, regardless of individual genotype, suggesting urban land cover use could be a source of individual heterogeneity in survival. Female mallards with greater domestic ancestry primarily used urban developed land cover, raising questions about their ability to survive in rural habitat types primarily used by wild mallards. Increasing proportion of domestic ancestry was associated with significantly lower probability of initiating nest incubation, indicating early generational hybrids had low productivity. Sedentary behavior, use and selection of urban areas, and low incubation incidence related to domestic ancestry raises concern regarding hybridization between wild and domestic game-farm mallards. Molting and natal origins estimated from stable hydrogen (δ2H) isotopes predicted 72%–84% of adult females molted and 59%–77% of juvenile females hatched at the latitudes of the Great Lakes region. Emigration likely contributed little to population decline as 98% of surviving female Great Lakes mallards remained in or returned to the Great Lakes region in subsequent breeding periods. The IPM identified declining productivity and increasing natural mortality in adult and juvenile female mallards as the primary demographic drivers of population decline. Productivity was lowest at urban developed banding sites in the southern Great Lakes region, where prevalence of hybrid mallards was greatest. Productivity declined with loss of area enrolled in the Conservation Reserve Program within Michigan and Wisconsin during 2000–2022. Natural mortality was 3.5–6.7 times and 1.3–4.2 times greater than harvest mortality for adult and juvenile female mallards, respectively, suggesting environmental factors during spring and summer, not harvest, drove annual mortality for female mallards. Attempts to increase or maintain Great Lakes mallard abundance should consider regional quantity and quality of nesting and brood-rearing habitat types and population genetics.
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