Apparent Survival and Local Movements of Harlequin Ducks Wintering at Isle au Haut, Maine

Abstract

Capture-recapture data from a five-year field study of individually marked Harlequin Ducks (Histrionicus histrionicus) wintering at Isle au Haut, Maine was used to examine patterns in age- and sex-specific apparent survival and local movements. Adult females had lower annual apparent survival probabilities than adult males. Survival probabilities for adult females were lower during the summer season than the winter season. Adult males showed no differences in apparent survival between the summer and winter intervals and survival during the winter season was similar for adult males and females. There was little evidence to suggest differences in apparent survival between first winter males and females, although sample sizes, especially for first winter females, were small. Annual apparent survival rates were lower for first winter males than adult males and likely reflected a combination of greater dispersal and higher mortality. Adult males captured in April in the study area disappeared from the study area more than adult males captured in November and may represent spring dispersal of unpaired males searching for mates or individuals from other wintering sites gathering before spring migration. Greater dispersal of adult and first winter males to adjacent wintering sites in subsequent winters was noted than for adult females.