Breeding and mortality of Oriental White-backed Vulture Gyps bengalensis in Punjab Province, Pakistan

Abstract

Populations of Oriental White-backed Vulture Gyps bengalensis and Long-billed Vulture G. indicus declined in India between the mid 1980s and late 1990s. Regional reports from India described declines of 95–100% across a wide area. This study was conducted to investigate the breeding success and pattern of mortality in two vulture colonies (Dholewala and Changa Manga) within Punjab Province, Pakistan between December 2000 and June 2001. Breeding success was found to be 62% in Dholewala and 59% in Changa Manga. A total of 668 sick and dead vultures were collected of which 591 were less than one month post mortem. No significant variation was found in the weekly mortality rate of adult and subadult vultures during the study period spanning winter through summer. A peak in mortality rate was observed during late April and early May that corresponded to mortality of newly fledged juveniles. Minimum annual mortality rate in the adult breeding population was calculated to be 11.4% and 18.6% in Dholewala and Changa Manga respectively. In a subsample of dead vultures (n = 185) visceral gout was found in 80% of adults, 63% of subadults, 19% of juveniles and 13% of nestlings. These mortality rates were consistent with a rapid population decline. Results imply that the mortality factor responsible for the decline in Gyps vultures described in India is also present in Pakistan and will potentially lead to a population decline of a comparable magnitude.