Effect of Drought on a Breeding Population of Wedge-tailed Eagles Aquila audax

Abstract

The number of pairs of Wedge-tailed Eagles Aquila audax breeding and their breeding success were assessed over a range of seasonal conditions from 1980 to 1985 near Menindee, in western New South Wales. The number of eagles breeding varied from 10-12 pairs during favourable years to three pairs during drought. Overall, the number of eagles breeding was not significantly correlated with both the density of Rabbits Oryctolagus cuniculus and the pasture biomass two months before laying, at hatching and at fledgling, and with the rainfall over the six months preceding these events. Few pairs bred when Rabbits were scarce but when Rabbits were abundant the number of eagles breeding did not exceed 12 pairs. Presumably the response by eagles to high densities of Rabbits was limited by the territoriality of the eagles. Breeding success averaged 0.99 chicks per pair and remained high during drought.