American black duck populations have declined by as much as 60% on the wintering grounds and continue to be a species of management concern. There are several possible explanations for this decline, of which one is loss of wintering habitat acreage and/or quality. Our current understanding of migratory and wintering waterfowl ecology suggests that availability of food for energy is the primary factor limiting waterfowl populations during winter and migration. Despite the historic and continued degradation of tidal marsh habitat in the Atlantic flyway, wintering black duck numbers have stabilized in the northern portion but severely declined in the southern portion (south of NJ) of their range. My research will estimate carrying capacity by measuring food resources and habitat use in Chesapeake Bay Virginia where black duck populations have dramatically declined. I will compare results to a previous study conducted on Long Island, NY to determine if winter food availability may be limiting black duck populations on the southern part of their winter range. In addition, this information will be used to model carrying capacity across the flyway.