Holley Shelter (KwaZulu-Natal, South Africa), a haven for breeding Southern Bald Ibises <i>Geronticus calvus</i> and other birds since the Late Pleistocene

Abstract

Cliffs are attractive roosting and breeding localities for numerous birds, which develop diverse modes of interaction ranging from avoidance to competition, and predation of chicks in their nests. The preservation of bird remains from archaeological deposits adjacent to a ∼20 m cliff at Holley Shelter, on the Fountainhill Estate in KwaZulu-Natal, South Africa, offers a rare opportunity to document such interactions in the past. A comparison of archaeological data with modern, seasonal sightings of birds at the cliff underlines a strong degree of continuity in the composition of the local avian community. In particular, we document the presence in the Late Pleistocene of a diverse bird association, which includes the White-necked Raven Corvus cf. albicollis, other cliff dwellers (Apodidae, Accipitridae, Tytonidae, Falconidae), as well as Phasianidae, Columbidae, and small to medium non-identified passerines. Additionally, we present the oldest documented fossil record of the Southern Bald Ibis Geronticus calvus, a Near Threatened southern African endemic with a modern distribution restricted to high-altitude grasslands in the eastern parts of South Africa, Lesotho and eSwatini. At Holley Shelter, the discovery of Southern Bald Ibis fossil remains, including those of unfledged birds, allows us to infer that a breeding colony occupied the cliff 35 000 years ago – as they still do today. It indicates the Late Pleistocene occurrence around the site of dry and mostly treeless grasslands, perhaps exposed to regular wildfire. The taphonomic analysis of the bird assemblage illustrates the implication of diurnal birds of prey in the accumulation of some of the bird remains in the archaeological deposits.