Waterbird diversity, densities, communities and seasonality in the Kalahari Basin, Botswana

Surveys in all major wetlands in Botswana (52,127 birds of 104 species on 1 0,672 ha of water and along 1782 km of shoreline) showed that waterbird div ersity (from rarefaction) and densities were highest at small ephemeral end orheic pans. Oligotrophic waters in the Okavango Delta had similar diversit y, but 10 times lower density. Large saline pans and highly eutrophic sewag e ponds supported high densities, but the lowest diversity. Man-made dams w ere intermediate. The Chobe floodplains and mesotrophic backwaters in the O kavango were the only important dry season refuges found; many waterbirds l eave the country during dry periods. Ephemeral pans constitute the most imp ortant wetland system for birds in the Kalahari Basin. (C) 1999 Academic Pr ess.