Body condition of American black ducks (Anas rubripes) wintering in Atlantic Canada using carcass composition and a scaled mass index

Body condition is commonly used in ecology to assess the physiological health of an organism or population and can be used to predict individual survival or breeding success. Waterfowl have been the focus of much research on body condition, and we studied body condition via carcass composition and using a scaled mass index (SMI) in American Black Ducks (Anas rubripes Brewster, 1902) wintering in coastal, agricultural, and urban areas of Atlantic Canada. Carcass composition varied between sexes and body mass decreased through winter as fat reserves depleted. Carcass composition was compared with American Black Ducks wintering in the United States, and American Black Ducks wintering in Atlantic Canada were structurally smaller yet proportionally fatter than those wintering in the United States, likely as a mechanism to survive Atlantic Canada's harsher winters. SMI did not differ between coastal, agricultural, or urban American Black Ducks, indicating that despite known differences in the diets of the Black Ducks from these three areas, they can maintain similar body conditions capable of surviving the winter. We show that the SMI is a nondestructive alternative to study body condition in waterfowl. Our research highlights the adaptability and hardiness of American Black Ducks at the northern limit of their winter range.