Population estimates of three vulture species in Kruger National Park, South Africa

Abstract

Vultures are globally threatened, yet reliable population data on these birds are few, thus measuring their response to change is difficult. Kruger National Park (KNP) in South Africa is an important stronghold for many avian species, particularly vultures. In this study we generate population estimates for three vulture species in KNP using two plotless density estimators (PDE): a distance estimator based on nearest-neighbour distance and T-square sampling. We flew aerial censuses over large (c. 3 500 km²) sample areas in two ecogeographically separate parts of KNP and counted vulture nests visible within predetermined transects. In total 416 White-backed Vulture Gyps africanus, 22 Lappet-faced Vulture Torgos tracheliotos and 24 White-headed Vulture Trigonoceps occipitalis nests were recorded. The nearest-neighbour distance PDE performed poorly, and we used a T-square PDE calibrated with aerial survey counts to extrapolate across KNP and estimate breeding population sizes. There are an estimated 904 (95% CI ± 162) pairs of African White-backed Vultures, 78 (95% CI ± 18) pairs of Lappet-faced Vultures and 60 (95% CI ± 13) pairs of White-headed Vultures in KNP. These results provide a basis for investigating how large vultures respond to ecosystem change and understanding their resilience within a broader environmental change scenario.

OSTRICH 2013, 84(1): 1–9