Effects of drought on birds in the Kalahari, Botswana

Results are presented from point-counts at six sites in the Kalahari in Botswana. Counts were repeated three times: during a dry season following good rains (1991), during the next wet season when rains were far below average, and the following dry season (1992) when the area became drought-stricken. Compared to the wet season, bird numbers decreased during the drought by 37–81% and species by 8–52%; compared to the previous dry season, birds decreased by 5–71% and species by 2–47%. Bird diversity (relative to numbers) tended to increase during the wet season but was little affected by drought, except in the northern Kalahari, where a greater proportion of birds moved out in response to drought. This gave the northern Kalahari the most distinct bird community during a wet cycle, but it became again typically Kalahari during the drought. Thus, the typical Kalahari bird communities expanded their range during drought into the moister periphery. Changes in numbers, most probably resulting from (local) movements were found in many species. Most confirmed earlier reports on their nomadic nature but some, like Red-crested Lophotis ruficrista and Northern Black Afrotis afraoides Korhaan, Chestnut-vented Tit-Babbler Parisoma subcaeruleum, Ant-eating ChatMyrmecocichla formicivora, Tinkling Cisticola Cisticola rufilatus, Black-chested Prinia Prinia flavicans, Marico Flycatcher Bradornis mariquensis and Brown-crowned Tchagra Tchagra australis have not been or are not widely recognised as mobile species. Ostrich 2004, 75(4): 217–22