WINTER DIET AND WEIGHTS OF BARROWS AND COMMON GOLDENEYE IN SOUTH-CENTRAL WASHINGTON

Little data are available relative to diets and body weight dynamics o f wintering Barrow's and common goldeneyes in freshwater habitats, and no data exist for subadults. Diets of these birds were studied on the Columbia and Yakima Rivers in southcentral Washington from October th rough May 1955-1956 and 1956-1957. Trichopteran larvae accounted for m ore than 67% of common goldeneye and 81% of Barrow's goldeneye food bi omass. Mollusc and aquatic plant achenes were other important food ite ms. Average weights of common goldeneye ranged from 599.3 +/- 39.86 g for subadult females to 1060.2 +/- 33.36 g for adult males. Average we ights of Barrow's goldeneye ranged from 736.0 +/- 44.73 g for subadult females to 1330.5 +/- 18.69 g for adult males. Body-weight dynamics o f birds may reflect resource availability, competition, and bioenerget ics, all of which may influence winter distribution, differential migr ation and habitat use by sexes.