Sexual differences in the foraging behaviour of Crested Shrike-tits, Falcunculus frontatus, during winter

Abstract

Sexual differences in foraging behaviour are common among bark-foraging birds. I compared the foraging behaviour of male and female Crested Shrike-tits, Falcunculus frontatus, a species well known for its bark-tearing habits, at two localities in the Northern Tablelands of New South Wales during winter. At both Wollomombi Falls and Armidale males visited dead branches and large coiled ribbons of bark more than females, while the latter concentrated on leaves, petioles and galls. There were no significant differences between the sexes in foraging heights at Wollomombi Falls but at the Armidale sites, 40 km away, females foraged significantly more at upper levels than males. Males took larger prey than females, but there were no significant sexual differences in the taxonomic composition of prey, with insect larvae comprising half of the diet, and adult beetles and spiders making up much of the remainder. This study provides further evidence of substantial variation in intersexual niche differentiation at both regional and local scales, and suggests that the availability of decorticating bark may be an important determinant of such variation in this species. While sexual dimorphism may partly account for sexual differences in the foraging niche of shrike-tits, it is possible that interference competition for food (via male dominance) and/or cultural transmission of sex-specific behaviour play a role in its maintenance.