Observations on the breeding biology of D’Arnaud’s Barbet Trachyphonus darnaudii

Abstract

Breeding behaviour is a key process for avian fitness and evolution, but the basic natural histories of many species are unknown. We studied the breeding biology of D’Arnaud’s Barbet Trachyphonus darnaudii (family Lybiidae) on the Usangu Plains in southwestern Tanzania. The birds excavated a vertical tunnel into the soil, expanding into a nesting chamber about 46 cm below the surface. Nests were located in small territories (between 500 and 10 000 m²) defined by song perches visited for duetting (and sometimes for chorusing). Probing the nesting chambers with a wireless endoscope camera enabled the first images of the eggs and the young of this species in the wild. On average, the clutch size was 3.8 eggs, birds incubated for 15.3 days, the nestling period was 28 days, and 2.5 young fledged from a nest. The nestlings were mainly fed insects, which may explain why the birds breed during the wet season (when insects are abundant) despite the potential risk of the subterranean nests being flooded.