The diet of shags Phalacrocorax aristotelis during the chick-rearing period assessed by three methods

Abstract

This paper describes a study of the diet of Shags using regurgitations by chicks, stomach contents and pellets collected concurrently. Sandeels predominated in all collections. Non- and failed breeders took a wider food spectrum than did chicks. Although adults fed their chicks almost entirely on sandeels, they themselves ate some fish from other fish families and probably digested these before they returned to the colony. Pellets are easy to collect and are useful to detect gross changes in diet of full-grown, but possibly non-breeding, Shags between years or colonies. Otoliths recovered from pellets cannot be used for age determination or back-calculations of size of sandeels eaten by Shags. Regurgitations can be used to describe the diet of chicks. There is no easy way to determine the diet of adults feeding chicks