Trophic, energetic, and physiological responses of wintering white-winged scoters (Melanitta fusca) to habitat variation

I examined diet, body condition, morphology, and physiology of white-winged scoters in relation to widely varying habitat conditions among wintering sites along the Pacific coast of British Columbia and northern Washington. White-winged scoters mainly consumed bivalves across all study sites, but showed flexibility to consume alternative prey in response to temporal changes in food resources. Scoters wintering at a highly exposed and unpredictable offshore site had higher lipid and body masses and different digestive morphology than birds at less exposed sites. Baseline corticosterone and plasma metabolites did not vary in response to differences in habitat conditions across sites. Collectively, these results suggest that wintering white-winged scoters achieve physiological homeostasis by varying diet, endogenous reserves, and gut morphology in response to differences in winter feeding sites.