Morphological Variation among Harlequin Ducks in the Northwest Atlantic

Harlequin Ducks (Histrionicus histrionicus) were captured and measured at a variety of staging, breeding, molting and wintering sites across their Northwest Atlantic range from 1996-2002. The consistency in the body measurements taken on the same birds across time and sites, as indexed by repeatability, was adequate (0.4-0.75), with the notable exception of total tarsus, which showed poor repeatability. Correlations among morphological measurements were weak within each sex. Some differences among locations were detected, notably in wing length, with birds breeding in Labrador showing longer wings than birds breeding further south and those wintering in Maine. Overall, however, major differences among sites were not apparent. Recent satellite and banding information indicate that many of these locations are linked and these observations are supported by this morphological data. Harlequin Ducks are similar to other ducks (except eiders) in that they are wide ranging and have disjunct populations, but show, at best, weak morphological differentiation across their range.