Factors Affecting the Diet of Crested Terns, Sterna-Bergii

Abstract

For crested terns, Sterna bergii Lichtenstein, changes in the accessibility of prey may cause changes in the composition of the terns' diet during the course of the tidal cycle, or in where and when the terns hunt. Some active selection of prey may also occur, for the terns feed fish of different sizes to chicks of different ages. Furthermore, some adults may hunt in specific places at specific times since many of the prey species are site-specific and are accessible only at certain times during the tidal cycle. More skill may be required to catch prey species that dwell on the bottom or in mid-water than those that dwell at or near the surface. We did not find a strongly consistent pattern in the times at which the terns feed their chicks, which may reflect the terns' opportunistic foraging habits.