THE DIET OF SHAGS PHALACROCORAX-ARISTOTELIS DURING THE CHICK-REARING PERIOD ASSESSED BY 3 METHODS

This paper describes a study of the diet of Shags using regurgitations by chicks, stomach contents and pellets collected concurrently. Sande els predominated in all collections. Non- and failed breeders took a w ider food spectrum than did chicks. Although adults fed their chicks a lmost entirely on sandeels, they themselves ate some fish from other f ish families and probably digested these before they returned to the c olony. Pellets are easy to collect and are useful to detect gross chan ges in diet of full-grown, but possibly non-breeding, Shags between ye ars or colonies. Otoliths recovered from pellets cannot be used for ag e determination or back-calculations of size of sandeels eaten by Shag s. Regurgitations can be used to describe the diet of chicks. There is no easy way to determine the diet of adults feeding chicks.