The Changing Sizes of Critically Endangered White-Backed Vulture Breeding Colonies Around Kimberley, South Africa

Abstract

INTRODUCTION The White-backed Vulture (Gyps africanus; WbV) is critically endangered (BirdLife International 2017) and has declined by up to 90% across parts of its range over the last 30 years (Ogada et al. 2016). It is a tree-nesting species that tends to congregate in groups for breeding (Mundy, Butchart, Ledger & Piper 1992) and aerial surveys of these breeding areas offer a reliable and repeatable means of assessing local population changes (Howells & Hustler 1984) that can complement results from road transect surveys (Herremans & Herremans-Tonnoeyr 2000). Near Kimberley in central South Africa, breeding WbVs have been at least partially monitored since the 1960s (Forrester 1967). The only aerial survey of this population in 2001 yielded an estimated breeding population of 240 pairs (Murn, Anderson & Anthony 2002) across six colonies. The 2001 estimate was more than double the previous estimate of 110 pairs (Anderson & Maritz 1997); at that time, the breeding colonies at Kimberley represented nearly 7% of the national population estimate of 3500 pairs (Anderson 2000). Since 2001, however, the population status of all the breeding colonies of WbVs near Kimberley is unknown. There are no published studies that describe trends longer than 10 years for WbV populations in South Africa. Numbers of breeding WbVs appear to have declined in some areas (Murn et al. 2013) but increased in others (Hitchins 1980; Bamford et al. 2009). Thus, there is a need for long-term (>10 years) data to assess population trends of endangered vultures. Here we present results from aerial surveys of the WbV breeding colonies at Kimberley in 2014 and compare the results to those from 2001.