What precipitates influxes of wetland birds to ephemeral pans in arid landscapes? Observations from Namibia

Abstract

Simmons, R.E., Barnard, P.E. & Jamieson, I.G. 1998. What precipitates influxes of wetland birds to ephemeral pans in arid landscapes? Observations from Namibia. Ostrich 70 (2): 145–148

The ability of wetland birds to rapidly find and exploit ephemeral pans is well known in and lands, but the episodic nature of such events means that the methods employed are poorly understood. Birds may: (i) wander randomly until wetlands are found; (ii) predict rainfronts and rainfall using changes in pressure gradients as cues; or (iii) follow rainfronts directly and descend onto pans as they fill. Observations from isolated pans in Namibia during the first rains indicate that wetland birds follow rainfronts, and descend onto pans as they fill. In one 30 ha pan, 37 birds of 5 species had arrived one day after filling and in another 50 ha pan over 300 birds of 13 species were attracted within 3 days of filling. Wetland birds, like migratory raptors, therefore, follow rainfronts, andMaywander locally thereafter. How species such as grebes and flamingos that exploit these pans for later breeding and intercontinental movements (respectively) time their flights to coincide with fully flooded pans remains unknown.