Diet of the imperial cormorant Phalacrocorax atriceps: Comparison of pellets and stomach contents

Abstract

A total of 45 pellets from the Imperial Cormorant or Blue-eyed Shag Phalacrocorax atriceps was collected in January 1994 at Duthoit Point, Nelson Island, South Shetland Islands. The analysis showed fish as the main prey, followed by octopods, polychaetes and gastropods. Notothenia coriiceps formed the bulk of the diet, but Harpagifer antarcticus was the most frequent and important fish in number. The prey items represented in the pellets were consistent with those observed in stomach contents sampled simultaneously in the same colony; however, they differed in importance. A daily mean of 0.7 pellets per bird was collected, representing 255 g of fish. Correction factors previously estimated in a feeding trial were applied to this value, and suggested that the average daily amount of food ingested by an adult cormorant during the sampling period was 1325 g, which falls within the range observed by stomach content analysis. Other aspects related to the feeding behaviour of the species are also discussed.