The Foraging Ecology of Birds of Eucalypt Forest and Woodland. I. Differences Between Males and Females

For six of nine species of sexually dichromatic, insectivorous birds of eucalypt forest, there were significant intersexual differences in foraging ecology. The most pronounced differences between sexes were in foraging height distribution (five species). Three species showed differences between the sexes in the behaviour used to capture prey, while males and females of four species differed in their use of foraging substrates. Differences were most pronounced among bark-foragers and least among ground-foragers. Intersexual differences in foraging by eucalypt forest birds appear to be a general phenomenon and one that is not necessarily associated with morphological differences nor with differences in reproductive roles. Among species with little morphological difference between the sexes, divergence between the sexes in foraging is most easily accomplished by foraging at different heights. This exposes each sex to a different array of substrates and leads to the use of different prey-attack behaviours. Ground-foragers do not have these options and therefore show little or no difference between the sexes in foraging ecology. Foraging data were obtained from three plots which differed in vegetation structure and floristics. Often differences in foraging ecology between plots were more pronounced for one sex, and males and females did not always change their foraging behaviour to the same extent or in the same direction. Combining the data from the different plots reduced the differences between the sexes in foraging ecology. Differences in the response of males and females to changes in habitat structure or resource availability may be an attribute of male/female differences in foraging behaviour, but such differences cannot be quantified from studies at a single location or time.