Black Duck Habitat Occupancy Trends in the Chesapeake Bay

Abstract

Changes in watershed land use, loss of coastal habitat to human development, and changing rainfall patterns have been attributed to waterfowl population declines in estuarine wintering grounds. We created a dynamic occupancy model for American black ducks (Anas rubripes) in the Chesapeake Bay to investigate relationships between occupancy, estuarine stressors, and wintering habitat from 1993-2019. Our model showed that wetlands and water clarity had a positive association with site colonization, whereas nitrate and nearby urban development had a negative association. Wetlands also had a strongly positive association with site persistence. Black ducks disproportionately occupied sites on the eastern shore and rarely colonized sites outside this zone. This propensity increased over time, with the population centroid/center of mass experiencing a small, but significant, shift eastward. These results highlight a “core area” of black duck habitat in the Chesapeake Bay that is vulnerable to large disturbances and should be prioritized for black duck population conservation.