The Effects of Spraying Deltamethrin Against Tsetse Flies on Insectivorous Birds in the Okavango Delta, Botswana

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2003-10-22

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I investigated the effects of spraying deltamethrin for tsetse fly control on bird populations in the Okavango Delta, Botswana. Because deltamethrin has low toxicity to vertebrates, effects on birds would have been indirect and caused by reductions in insect food supplies, not by poisoning. The northern half of the Delta was sprayed in 2001 and the southern half in 2002. I monitored resident bird populations at four sites (two in each spray block), using point counts. Birds were classified by diet as insectivorous or non-insect-dependent in order to check for declines in insectivorous. Sections of the 2002 spray block burned before the spraying started. In the 2001 spray block, there were no declines of insectivorous birds, and varied results for non-insect-dependent birds. In the 2002 spray block, the Chitabe site showed declines in insectivorous forest birds, which were not strongly correlated with the spraying, and Nxaraxa showed no such declines.

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