Food and Feeding Biology of the Common Tern during the Nonbreeding Season in Samborombon Bay, Buenos Aires, Argentina

-Common Terns (Sterna hirundo), which breed in North America and migrate into the southern hemisphere in winter, show a wide nonbreeding distribution that includes the Atlantic coasts of Argentina and Brazil. At Punta Rasa (Samborombon Bay, Argentina), there were about 30,000 Common Terns. Their diet in winter was assessed by the analysis of regurgitated pellets collected at Punta Rasa. Adult Coleoptera, Odonata, Orthoptera and Hemiptera were the main insects found in the diet. A total of 14 species of fishes were identified. Argentine Anchovy (Engraulis anchoita) and Anchovy (Anchoa marinii) (Family Engraulidae), represented 79% by number and the 78% of the consumed biomass of fish prey. The average length of fish prey was 90.0 ? 17.6 mm. Half the prey lived in seawater, while the other half was taken in estuarine or seawater. There was no evidence of fish prey taken by terns foraging in freshwater habitats. Total consumption of food was estimated as 106 tons of fish (most of themjuvenile) during a five month period at Punta Rasa. Received 6 August 2000, accepted 9 December 2000.