Nutritional budgets in free flying birds: Cedar waxwings (Bombycilla cedrorum) feeding on washington hawthorn fruit (Crataegus phaenopyrum)

Abstract

1. 1. Nutritional balances for calories, glucose, water, nitrogen, Na+, K+, Ca2+, and Mg2+ have been estimated for free-flying cedar waxwings feeding on Washington hawthorn fruits.2. 2. Birds assimilate 39.9 calories/fruit ( = 20.0% of available calories) and a net loss of 155mg of water/fruit.3. 3. Reducing sugars account for 74.5% of assimilated calories ( = 66.0% assimilation efficiency).4. 4. While feeding on these fruits, birds exhibit positive nitrogen and caloric balance, and negative Na+, K+, Mg2+, Ca2+, and water balances.