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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) 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 to black ducks wintering in the United States, and 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 black ducks, indicating that despite known differences in the diets of the 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 black ducks at the northern limit of their winter range.

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American black ducks, native to eastern North America, have been the focus of significant international conservation and management programs. The combined USA and Canadian population has traditionally been managed as a single population; however black duck demographics may vary by region. To help understand potential regional differences in black ducks, we used satellite telemetry to assess migratory chronology and movements of black ducks wintering near Windsor, Nova Scotia, Canada, near the northern limits of their wintering range where numbers are increasing. Wintering black ducks from Nova Scotia did not leave the Atlantic Flyway and included both longer‐distance migrants (~ 1500 km north) and locally‐breeding individuals. None of our tracked ducks travelled south of Nova Scotia during any part of the annual cycle, indicating a population segment that never leaves Canada and is subject solely to Canadian harvest pressures. Band recovery data revealed that a small portion (2.4%) of black ducks originally banded during winter in Nova Scotia were recovered south along the east coast of the USA, indicating that some of these black ducks are subject to international harvest pressures. Our results show that there are differences in annual black duck movements even within a small part of their range, adding to the growing evidence that black duck populations show fine‐scale temporal and spatial structure. This structure will need to be considered in future interprovincial and international harvest management plans of this important species.