ROLE OF FOOD IN TERRITORIALITY AND EGG PRODUCTION OF BUFFLEHEADS (BUCEPHALA ALBEOLA) AND BARROW'S GOLDENEYES (BUCEPHALA ISLANDICA)

Abstract

Abstract Buffleheads (Bucephala albeola) and the North American population of Barrow's Goldeneyes (Bucephala islandica) typically breed in boreal and montane regions where food is less available relative to most habitats used by temperate nesting ducks. We investigated diets and digestive organ morphology of sympatrically breeding female Buffleheads and Barrow's Goldeneyes in central British Columbia. Because those congeners exhibit interspecific aggression in defense of breeding territories, we predicted that competition for food could be a principal factor in evolution of that behavior. We also hypothesized that breeding Buffleheads would show greater variation in digestive organ morphology than Barrow's Goldeneyes because of their smaller body size and consequently greater reliance on their diet to meet nutritional requirements for egg production. Both species fed predominantly on aquatic insects during all reproductive periods, particularly larvae of damselflies (Zygoptera), midges (Chironomidae), and...