Doves, pigeons, and sandgrouse are notably wary in approaching the isolated and usually exposed, open water holes where they congregate in large numbers to drink in desert regions, as, for instance, in parts of Australia (Cameron, 1938) and Africa (Bowen, 1927). What are the hazards which make such obvious behavior of adaptive significance in the lives of these birds? During fieldwork carried out between 18 and 23 January and between 5 July and 11 August 1964 in the Namib Desert, I had frequent opportunities to observe flocks of columbiform birds drinking at a water hole in the dry bed of the Kuiseb River and to gain some insight into the role which diurnal raptors play in determining their approach to water.