Factors influencing the breeding performance of the Augur Buzzard Buteo augur in southern Lake Naivasha, Rift Valley, Kenya

Abstract

The breeding performance of the Augur Buzzard Buteo augur in 1995–1998 was compared between three different areas south of Lake Naivasha, Kenya. These were: (1) a national park (Hell’s Gate), (2) an undisturbed Acacia woodland-pasture (Mundui) and (3) an intensively farmed horticultural area (Sulmac-Oserian). Augur Buzzards in Mundui had the most optimal nesting habitat, produced the most fledglings (1.6 chicks per year), enjoyed an abundant food supply as their land was not heavily grazed, and suffered the least persecution. In contrast, Augur Buzzards in Hell’s Gate produced the fewest fledglings (0.5 chicks per year). Their food supply was not abundant and their nests were confined to cliffs and short shrubs making them vulnerable to predation. Augur Buzzards in Sulmac-Oserian performed intermediately, producing 0.8 chicks per year and suffering the highest adult mortalities (12%) from human persecution. Height of grass in fields within a pair’s territory was the most important variable in predicting whether Augur Buzzards attempted to breed or not. Mean annual adult mortality was lowest at Mundui (4.8%) and highest at Sulmac-Oserian (12%). Adult mortality and the success of previous breeding attempts were the most important predictors in determining breeding performance.

Ostrich 2009, 80(1): 9–17