Prospecting for Nest Sites by Cavity-Nesting Ducks of the Genus Bucephala

We studied the pattern of post-laying visitation of nest sites by non-nesting females in three species of cavity-nesting ducks, the Common and Barrow's goldeneyes (Bucephala clangula and B. islandica) and the Bufflehead (B. albeola). Nests were visited from mid-June to mid-July when most nesting females either had hatched their clutches or were finishing incubation. Females often visited more than one nest site and each nest site could be visited by several birds. Observations of marked individuals and body measurements of trapped birds show that most visiting females were either yearlings or failed breeders. These females always visited nest sites in intra- or inter-specific groups, and exhibited typical vocalizations and flight patterns. We propose that these females were "prospecting" for nest sites in preparation for the next breeding season. We could not find any detrimental effects of prospecting on incubating females. We also discuss the evolutionary significance of prospecting behavior and its relationship to delayed maturity and nest-site availability for both cavity- and ground-nesting North American ducks.