Abstracts

Presented by Aidan Flores - Email: aflore06@syr.edu

Availability of winter habitat and forage for American black ducks (Anas rubripes; hereon black ducks) can be limiting. Increasing urbanization, sea level rise, and other stressors often make restoration of coastal marshes infeasible or logistically difficult. Agriculture fields may need to increasingly serve as winter foraging sites for black ducks. We determined if diets, body condition, and stress indices of black ducks and mallards (Anas platyrhynchos) differed between agricultural and coastal sites on Long Island, New York. We captured black ducks and mallards at agricultural sites and lethal collections at coastal marshes. Agricultural fields were used by mallards (61% of ducks) and black ducks (36% of ducks), but only black ducks were observed in coastal marshes. Black ducks had 14.8% greater 15C ratios at agricultural than coastal sites, whereas 15N ratio showed the opposite trend. Black duck and mallard 15C and 15N ratios were similar at agricultural sites. These results suggest that diets differed between cover types for black ducks, but not between species at agricultural sites. Adjusted body mass of black ducks at coastal (1,081.1 36.8 g) and agricultural (1,114.6 15.6 g) sites were similar, but mallards (1,180.7 26.0 g) were 5.9% heavier than black ducks at agricultural sites. Red blood cell percentages were greater at agricultural (53.1 0.9%) than coastal sites (40.6 2.3%) for black ducks, whereas there was no difference between black ducks and mallards (52.9 1.5%) at agricultural sites. There were no differences in heterophil/lymphocyte ratios by treatments or species. Our results do not suggest substantial benefits of corn supplements to black ducks wintering on eastern Long Island. However, black ducks feeding on corn were not in worse condition, suggesting that loss of coastal marshes could partially be offset by supplementing with agricultural grains during winter.