ANNUAL DIET OF CEDAR WAXWINGS BASED ON US BIOLOGICAL SURVEY RECORDS (1885-1950) COMPARED TO DIET OF AMERICAN ROBINS - CONTRASTS IN DIETARY PATTERNS AND NATURAL-HISTORY

The diet of Cedar Waxwings (Bombycilla cedrorum) is described using re cords of gut contents collected by the U.S. Biological Survey. Cedar W axwings eat more fruit than most other Temperate Zone birds, including one of the most frugivorous thrushes, the American Robin (Turdus migr atorius; 84 vs. 57% fruit in their annual diets, respectively). Cedar Waxwings are almost exclusively frugivorous in the winter and early sp ring. During the spring period of fruit scarcity, flowers comprise a l arge portion of the diet of waxwings (44% of May diet). Cedar Waxwings eat aerial and vegetation-borne animal prey, whereas American Robins eat vegetation-borne and terrestrial prey. The fruits eaten by Cedar W axwings are characterized by high sugar and low lipid content. America n Robins, like other North American thrushes, eat sugary and lipid-ric h fruits, suggesting contrasting digestive strategies in waxwings and thrushes. This perspective is reinforced by the correspondence between these birds' diets, the timing of breeding in relation to availabilit y of preferred foods, and flocking patterns.