Trends in Waterbird Numbers in the Southern Rift Valley of Kenya, 1991-2000

Abstract

Abstract Coordinated waterbird counts have been carried out in major Kenyan wetlands annually over the last decade. The lakes of Naivasha, Elmenteita, Nakuru (counted since 1991) and Bogoria are close to each other in the southern Rift Valley and hold the bulk of both resident and migrant waterbirds counted each year. Levels of the four lakes fluctuate substantially and all but Naivasha are saline. By contrast, Dandora Ponds near Nairobi is a site with stable water levels. We compared trends in numbers of birds, categorized by family and by migratory status, with an earlier analysis in 1996 and between the fluctuating Rift Valley lakes and Dandora Ponds. Flamingo numbers remained highly variable at all sites, showing no long-term trends. In 1996, significant declines were found in many piscivorous waterbird groups, including grebes, pelicans, cormorants, storks, terns and gulls, mainly associated with falling lake levels at Lake Nakuru; by 2000, numbers had recovered. Consistent declines in rallids, birds...