Predicting population sizes and priority conservation areas for 10 endemic Namibian bird species

Namibia's avifauna includes at least 14 species currently classified as national endemics or near-endemics. Line transect sampling of 10 of these was undertaken over 7 months in 1996. For all species, significant regression relationships were obtained between calculated bird density and environmental variables (altitude, rainfall and vegetation type), and these relationships were used to predict bird abundance in each extant combination of environmental variables. A GIS was used to map predicted abundances, calculate population sizes and define species' distribution limits. Predicted population sizes ranged between 1848 and 1,501,029 birds, representing the first population estimates for southern African birds using this approach. For all species, total population size appears to be viable but protected areas exclude their core areas. A modified Shannon index was calculated to determine areas of highest diversity. Most diversity hotspots fall within the Escarpment vegetation zone, very little of which is protected. We emphasize the conservation importance of this zone.