Original Articles

Aspects of diet choice and digestion in the Dark-capped Bulbul Pycnonotus barbatus

Published in: Ostrich: Journal of African Ornithology
Volume 79, issue 1, 2008 , pages: 73–78
DOI: 10.2989/OSTRICH.2008.79.1.9.365
Author(s): ColleenT Downs

Abstract

Most avian frugivores are not specialised and feed on a variety of fruit that are generally nutrient dilute. Little is known about avian frugivores that supplement their diets with insects as a nutrient source. Although considered a frugivore, the Dark-capped Bulbul Pycnonotus barbatus feeds on insects opportunistically. Consequently food preference, intake rates and digestive efficiencies were compared on a nutrient-dilute fruit diet (apple) versus an insect diet (mealworm) and a combination of these. Transit times were also determined. Birds maintained body mass on the apple-only treatment but gained body mass on the mealworm and combination treatments. The apparent energy-assimilation coefficient varied significantly between treatments, being highest on the mealworm diet. Energy intake rates were higher on the mealworm diet. When offered a combination, birds chose mealworms in preference to apple and ate little apple. The results suggest that these frugivorous birds obtain adequate nutrients for maintenance from nutrient-dilute fruit but supplement their diet with insects or nutrient-dense fruit to obtain nutrients required for activities additional to maintenance.

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