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 10,672 ha of water and along 1782 km of shoreline) showed that waterbird diversity (from rarefaction) and densities were highest at small ephemeral endorheic pans. Oligotrophic waters in the Okavango Delta had similar diversity, but 10 times lower density. Large saline pans and highly eutrophic sewage ponds supported high densities, but the lowest diversity. Man-made dams were intermediate. The Chobe floodplains and mesotrophic backwaters in the Okavango were the only important dry season refuges found; many waterbirds leave the country during dry periods. Ephemeral pans constitute the most important wetland system for birds in the Kalahari Basin