The role of breeding range, diet, mobility and body size in associations of raptor communities and land-use in a West African savanna

Abstract

To provide insight into raptor declines in western Africa, we investigated associations between land-use and raptor distribution patterns in Cameroon. We examined the role of breeding distribution, species’ migratory mobility, diet, body size, and thus area requirements, on 5-km scale patterns of raptor richness and abundance. We recorded 15,661 individuals, comprising 55 species during road surveys, spanning four annual cycles. Results revealed evidence for the importance of National Parks (N.P.’s), natural vegetation, humans, and cotton in shaping raptor assemblages, but responses differed between functional groups and biogeographical zones. Human populations and natural habitat, interacting with zone, were important predictors of Afrotropical raptor richness, and N.P.’s of Palearctic raptor richness. Areas cleared of natural habitat in the Guinea zone had comparatively rich and abundant large, small sedentary and migratory Afrotropical raptor assemblages, but humans limited positive effects. Palearctic raptor abundance peaked at higher levels of human land-use than Afrotropical raptors. Vertebrate-hunting Palearctic raptor richness was positively associated with cropland, while cotton and human land-use in the Inundation zone had a stronger negative impact on insectivorous Palearctic raptors. Richness of large sedentary raptors declined with increasing distance to N.P.’s, contrary to communal scavenger richness, which increased with human populations. Humans, habitat loss and cotton in the Inundation and Sudan zones had similar, negative effects on small sedentary and small migratory Afrotropical raptor assemblages. We conclude that increasing human populations, natural vegetation loss, and expanding cotton will negatively affect the majority of Afrotropical and insectivorous Palearctic raptors, while vertebrate-hunting Palearctic raptors may benefit from cropland expansion.