Family Associations in a Breeding Colony of Critically Endangered Hooded Vulture (Necrosyrtes monachus) in the Lowveld of South Africa

Abstract

Numbers of Critically Endangered Hooded Vultures (Necrosyrtes monachus Temminck 1823) are declining across their distribution. The range-edge population in South Africa is one of the smallest populations with only 100–200 mature individuals. In South Africa, Hooded Vultures nest solitarily in loose colonies (mean distance between nests 0.76 km) along water courses. Basic ecological information, such as breeding behaviour, is still lacking for the species. In this study, we examine the relatedness and nest turnover of nesting individuals along the Olifants River and other locations in the Lowveld of South Africa by sampling nests over five consecutive years. A key hypothesis tested is whether communal roosting sites function as information-sharing hubs, a phenomenon that has been seen in Cape Vultures (Gyps coprotheres) and other cliff-nesting vultures. Theory suggests that information sharing occurs more frequently between closely related individuals. If true, we expect distance between nests and genetic relatedness to be positively correlated and individuals to use the same nests over multiple years. Naturally moulted feathers (n = 108) were collected below nests over five consecutive years, and 14 microsatellite loci markers were used to measure genetic relatedness. Mantel tests performed correlating distance between nests to relatedness coefficient estimators TrioML (r = 0.032, R² = 0.001, p = 0.224) and LynchRD (r = 0.007, R² = 0.00005, p = 0.403), found no statistical correlation. The Mantel test performed using Nei's genetic distance and distance between nests did show a negative correlation (r = −0.108, R² = 0.0117, p-value = 0.012), indicating that individuals that were more closely related tended to breed further away. No nest reuse was found in this study. We thus believe that these loose colonies do not act as food-finding hubs, but rather that the Olifants River is an important breeding site for these birds.