Observations on the population and breeding status of the African White-backed Vulture, the Black-chested Snake Eagle, and the Secretarybird in the Kgalagadi Transfrontier Park

Abstract

The breeding success of the nests of 60 African White-backed Vultures Gyps africanus, nine Black-chested Snake Eagles Circaetus pectoralis and 12 Secretarybirds Sagittarius serpentarius was monitored for three years, during a seven-year population dynamics study on raptors in the Kgalagadi Transfrontier Park (KTP). We also report on nest site selection, timing of breeding, population fluctuations and anthropogenic factors that affect mortality. On average, African White-backed Vultures produced 0.47 young per breeding attempt per year (ypby), Black-chested Snake Eagles 0.67 ypby, and Secretarybirds 2.2 ypby. Most African White-backed Vultures laid eggs in June, and both Black-chested Snake Eagles and Secretarybirds laid mostly in June and July. Mean nest heights were as follows: African White-backed Vultures 11m, Black-chested Snake Eagles 5m, and Secretarybirds 6m. Populations of Black-chested Snake Eagles and Secretarybirds fluctuated between years and in some years most of the populations moved away, especially during very dry periods. Anthropogenic threats include poisoning, drowning and roadkills.