Sugar-Tasting Ability and Fruit Selection in Tropical Fruit-Eating Birds

Publisher Website
Google Scholar
Abstract
The sugar-tasting abilities of four species of tanagers and two species of manakins were tested. Three tanager species were able to detect differences in diets containing 8%, 10%, and 12% sugar. In pairwise choice trials, they preferred the diet highest in sugar. Neither species of manakin discriminated among the three diets. This apparent difference in tasting abilities of tanagers and manakins may be a result of their fruit-handling techniques. Tanagers crush fruits in their bills, thereby releasing juices onto their tongues. Manakins swallow fruits whole; their tongues rarely encounter fruit juice. Hence, manakins' fruit-handling technique is poorly suited for sensing the taste cues in fruit juices. Variation in fruit sugar concentration is common within and among plant species and is great enough to be detected by birds. Birds probably have selected for sweeter fruits.