The foraging ecology of birds of eucalypt forest and woodland. I. Differences between mates and females

For six of nine species of sexually dichromatic, insectivorous birds of euc alypt forest, there were significant intersexual differences in foraging ec ology. The most pronounced differences between sexes were in foraging heigh t distribution (five species). Three species showed differences between the sexes in the behaviour used to capture prey, while males and females of fo ur species differed in their use of foraging substrates. Differences were m ost pronounced among bark-foragers and least among ground-foragers. Interse xual differences in foraging by eucalypt forest birds appear to be a genera l 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 s exes in foraging is most easily accomplished by foraging at different heigh ts. This exposes each sex to a different array of substrates and leads to t he use of different prey-attack behaviours. Ground-foragers do not have the se options and therefore show little or no difference between the sexes in foraging ecology. Foraging data were obtained from three plots which differ ed in vegetation structure and floristics. Often differences in foraging ec ology 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 th e same direction. Combining the data from the different plots reduced the d ifferences between the sexes in foraging ecology. Differences in the respon se of males and females to changes in habitat structure or resource availab ility may be an attribute of male/female differences in foraging behaviour, but such differences cannot be quantified from studies at a single locatio n or time.