Ecological Aspects of Common Goldeneyes Bucephala clangula Wintering on the Upper Mississippi River

Abstract

Roosting flight characteristics of common goldeneyes, B. clangula, were correlated with ambient temperature, wind direction, feeding area location and date. More birds remained near the communal roost during days when colder temperatures prevailed and early in winter when feeding was common by a brewery discharge outlet. Roosting populations declined under colder daily temperatures but increased during winter. Roosting sites were vacated temporarily by most birds in periods of extremely cold temperatures (< -25.degree. C). Daytime sex ratio counts were adult male biased throughout winter, indicating males returned to the roost site from feeding areas earlier in the day than did females. Adult males occasionally defended small individual foraging sites from intruding conspecifics of both sexes. Available data indicate that sexual segregation within habitats and between wintering areas is influenced by climatic effects interacting with several ecological factors: body size-weight-metabolic relationships, intersexual competion for food and sexual selection pressures.