Distribution patterns and conservation status of four bustard species (Family Otididae) in a montane grassland of South Africa Original Research Article

The abundance and distribution patterns of four threatened species of bustards (Eupodotis caerulescens, E. barrowii, E. melanogaster and Neotis denhami) in 3200 km2 of montane grasslands in the Wakkerstroom district, South Africa were characterised and related to altitude, topography and land use. During 2001 and 2002, 61 car-driven transects (544 km in total) were carried out to count bustards at the onset of the breeding season. The spatial patterns of land use and bustard occurrence along transects were characterised using geostatistics. The influence of explanatory variables on each species occurrence was assessed using logistic regression. There were inter-specific differences in distribution, with E. caerulescens occurring at higher altitudes than the other species. These differences were partly explained by different habitat preferences. Population estimates for the study area were ≈1400 E. caerulescens, 150 E. barrowii and 30 male E. melanogaster. The main threats for the bustard populations in the region are commercial afforestations (mainly for N. denhami) and agricultural intensification (mainly for E. barrowii and E. melanogaster). The results of this study can be used as a baseline situation against which future monitoring could be compared. The used method proved to be effective for characterising occurrence patterns and censusing bustard populations in relatively large areas, as well as describing large-scale habitat patterns.