Semester

Fall

Date of Graduation

2018

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

James T. Anderson

Committee Co-Chair

Christopher T. Rota

Committee Member

Christopher T. Rota

Committee Member

Michael L. Peters

Abstract

The American black duck (Anas rubripes) is a species of dabbling duck found only in the northeastern part of North America, and widely hunted until its decline. Since the 1950s, the total population has decreased by 53%. Habitat degradation and decline of wintering and breeding wetlands, historic overharvest, and interactions with the mallard (A. platyrhynchos) are attributed as some of the main causes of the black duck population’s decrease. Many policies and taxa- and habitat-specific joint ventures have since been created to aid in studying and improving North American wetlands and black duck populations throughout both their breeding and wintering range. However, limited research has been performed in the western reaches of the black duck’s wintering range, where 2.8 – 8.9% of the wintering population resides in habitats that are very different than the Atlantic core range of the black duck. As such, we examined wetland biomass and energy availability throughout the region using moist-soil seed production sampling and benthic core sampling, finding riverine systems provided the highest energy to wintering black ducks of all wetland systems, unmanaged wetlands provided the most energy of all management schemes, and modified wetlands provided the greatest energy of all levels of naturalness. Ultimately, we found Central Appalachia could provide for 1,077,805 – 1,916,452 black ducks throughout the winter. Additionally, we calculated time-activity budgets for wintering black ducks from behavioral observations and estimated daily energy expenditure using both a simple- and a complex-cost of thermoregulation component. We found that swimming was the most observed behavior overall, but that behavior varied among wetland systems, management schemes, levels of naturalness, and year. From this, we estimated daily energy expenditure with a complex-cost of thermoregulation of a wintering black duck in Central Appalachia to be 1,542.95 kJ/bird/day, which was 2.25 times higher than the estimation with a simple-cost of thermoregulation component. Lastly, we used single-season occupancy models and N-mixture models to determine drivers of black duck and mallard occupancy and abundances in the region. We determined that black duck occupancy was higher in passively managed wetlands, palustrine systems, and modified wetlands, and lower in the second year of the study. Black duck abundance decreased in the second year of the study and was higher in riverine and palustrine systems, modified wetlands, passively managed wetlands, and when beavers were present, as well. Meanwhile, mallard occupancy was positively associated with increasing surrounding developed land within 200 m of survey points. Mallard abundance was positively associated with actively managed wetlands, palustrine systems, created wetlands, and privately-owned wetlands. Both mallards and black ducks were positively associated with many surrounding land use types. From this research, we recommend that future research incorporates the complex-cost of thermoregulation component into energy expenditure calculations to acquire more refined estimates of duck-use days. We also recommend that managers follow strict water-level iii manipulation schedules to improve seed biomass in wetlands, focus on providing nearby diverse wetland complexes of varying management schemes, and incorporating passive management at currently unmanaged riverine wetlands.

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