Variation in nest predation among arid-zone birds
AbstractI examined the nesting habits and success of 11 co-existing species in an arid, sub-tropical habitat in South Africa. Nesting success ranged from 3.5% to 75.4% among species, with predation by mammals and snakes accounting for 94% of nest losses. Differences in predator avoidance behaviour (deserting the nest vs sitting tight) may explain markedly different daily nest predation risk experienced by the Double-banded Courser Rhinoptilus africanus (0.5%) and Namaqua Sandgrouse Pterocles namaqua (9.2%). Nest predation was inversely related to nest density, but this reverse density dependence may reflect a seasonal effect, as predation decreased as the breeding season progressed from spring to mid-summer. Overall, daily egg predation rates were higher than daily nestling predation rates among nine altricial species, contrary to the widely-held view that increased activity at the nest during the nestling period increases predation risk. The prediction of higher daily nest predation rates on ground-nesting species than on shrub/tree-nesting species in an open habitat was supported. Among ground-nesting species, territorial residents suffered significantly lower daily nest predation rates than nomads, suggesting that residents may use experience of local predator activity to place their nests in safer sites.
Ostrich 2004, 75(4): 228–235