A trait-based risk assessment of South African forest birds indicates vulnerability of hole-nesting species

Forests in South Africa are under threat from a variety of anthropogenic land use changes; however, the impacts of these changes on wildlife populations are poorly understood. To address this issue, a pan-European trait-based risk assessment framework was modified for use in South Africa. This framework allows the identification of habitats and species most at risk, as well as the most important threats to species' persistence. The original model was expanded through the addition of any positive effects of land use change on species, to create a net risk model. Range changes were predicted by risk scores in montane forests, where the major risks were found to be invasion by alien trees and bark collection for traditional medicine. Risk scores within lowland species were higher, indicating potential population declines not accounted for by the SABAP range change data, as well as greater risk in the near future due to land use changes. Five hole-nesting species of birds, out of only ten holenesting species included in the study, consistently emerged as having the highest risk scores overall, and across forest types: the black-bellied starling, Narina trogon, trumpeter hornbill, crowned hornbill and green barbet. Consistent with this, using the net method, nesting risk was found to be higher than foraging risk for species across all forest types and within each type, suggesting that land use changes in South Africa are rendering forestdependent hole-nesting species particularly vulnerable.