Reproduction of Bali starlings Leucopsar rothschildi at Durrell Wildlife Conservation Trust, Jersey

Abstract

The Critically Endangered Bali starling Leucopsar rothschildi is the only endemic avian species on the island of Bali, Indonesia. In 1998 the wild population comprised c. 25 birds, of which only eight to ten were wild born. An international captive‐breeding programme to restore a viable and self‐sustaining population in Bali was established in 1987. In order to understand better the reproductive activity of Bali starlings at the Durrell Wildlife Conservation Trust, Jersey, small cameras were placed inside the nestboxes of six pairs. Details of egg production and egg turning were recorded for 16 clutches, and incubation data were recorded for 14 clutches. Mean clutch size was 2·8±0·20 SE eggs. Females incubated eggs significantly more than ♂♂ (median 143‐6 hours vs 46·8 hours, ♀vs♂). During the day (0500–2100 hours) eggs were turned every c. 13 minutes. At night eggs were incubated by ♀♀ while ♂♂ roosted in the nestbox. The median duration of incubation was 15·5 ± 0·24 SE days. Behaviour of parents and chicks during hatch and rearing was recorded for seven broods. Hatching success was 68% and for each pair the mean brood size was two chicks. Females carried out significantly more brooding (t= 7·08, df=6, P<0·001), preening (t= 2·94, df=6, P= 0·025) and manipulation (t= 2·50, df=6, P= 0·046) of chicks than ♂♂. Males provided significantly more feeds (62%) than ♀♀ (38%) (t= 4.035, df=6, P= 0·006). Only five birds survived > 30 days, of which three were parent‐reared and two hand‐reared. All parents assisted chicks during hatching. Synchronous hatching was recorded for 45% of chicks. Nutritional requirements of chicks were higher during the first 9 days post‐hatch. Chick survival was compromised by parents feather plucking the chicks.