Sex-specific foraging behaviour of the Whiskered Tern (Chlidonias hybrida) during the breeding season

Abstract

Sexual size dimorphism is common in many bird species. It can lead to sex-specific differences in foraging ability. The Whiskered Tern (Chlidonias hybrida) exhibits sexual size dimorphism. Sex-specific differences in the foraging behaviour of Whiskered Terns were investigated in carp ponds during the breeding season. Foraging behaviour was different between the sexes. Males foraged mainly by shallow plunge diving into the water, while females foraged mainly by picking prey from plants and the water surface. We attributed these differences to sexual size dimorphism, as males are significantly larger than females. The foraging success of vertebrate prey capture by Whiskered Terns was high (male average = 61%, female average = 65%), and not significantly different between sexes. Males had more aggressive encounters than females. Generally, we did not find correlations between the rate of main foraging techniques of male and female Whiskered Terns and weather conditions (cloud cover and wind speed). This was probably due to the high prey availability in carp ponds.