Pesticide Residues and Eggshell Thickness of Griffon Vulture Eggs in Southern Africa

Abstract

Two species of griffon vulture forage over much of southern Africa, a subcontinent that is a patchwork of wildlife areas, ranching country, and industrial and agricultural development. The Cape vulture (Gyps coprotheres) is endemic to the region (Snow 1978), and recent research has shown that the species is declining, perhaps markedly (Mundy and Ledger 1977). Because birds of prey in other parts of the world are known to be vulnerable to pesticide residues (Ratcliffe 1970), it was necessary to examine this possibility in the vulture. Most of the Cape vulture population lives in South Africa, and this country is highly industrialized and intensively agricultural. Pesticides are a part of this environment, and our objective was to determine if they acted as yet another factor in the decline of the Cape vulture. The white-backed vulture (G. africanus) inhabits almost all of sub-Saharan Africa (Snow 1978). It is the most common species of vulture in the various game reserves of southern Africa, and is also numerous over much of the subcontinent's ranching land; it is not known to be declining (Mundy 1980).