Raptors drowning in farm reservoirs in South Africa

Abstract

Anderson, M.D., Maritz, A.W.A. & Oosthuysen, E. 1999. Raptors drowning in farm reserviors in South Africa. Ostrich 70 (2): 139–144

In the arid areas of southern Africa, the drowning of raptors in small reservoirs on farms is a significant cause of mortality. Records of 322 raptors of 29 species which drowned during 163 separate incidents have been collated. Whitebacked Gyps africanus and Cape Vultures Gyps coprotheres, and Martial Polemaetus bellicosus and Black Eagles Aquila verreauxii, were the species most frequently recovered from reservoirs. There are few records of small raptors (<300 g) succumbing in this manner. There are several possible explanations as to why raptors drown. The simplest is that these birds enter the reservoir to drink or bathe and if it is not full are then unable to climb up the structure's steep sides. There have been 12 recorded vulture mass drowning events, involving as many as 38 buds at one time. The reason for these mass drownings is probably different to the individual drowning of other raptors, with the “intimate lifestyle” hypothesis being the most plausible. There are simple, cheap and effective solutions to prevent the drowning of raptors and these are being advocated with success in the Northern Cape Province, South Africa.