Food and feeding ecology of Gull-billed Terns (Gelochelidon nilotica) in Greece

A study of the diet of Gull-billed Terns was carried out by analysis of regurgitated pellets during the breeding season in three Greek coastal wetlands : Evros Delta (1985-1987), Alyki Kitrous (1989) and Messolonghi (1989). In the Evros Delta, insects, especially Coleoptera, were the most important prey ; non-insect taxa (Bivalvia, Crustacea, Osteichthyes, Reptilia and Mammalia) were much less important. At Alyki, insects, especially Orthoptera, were the predominant prey whereas other prey items (Bivalvia, Amphibia, Aves, Mammalia) were of little importance. At Messolonghi, crabs (Carcinus sp.) were the prey most often consumed ; insects (mainly Orthoptera and Coleoptera) were less common in the diet and other prey types (Arachnida, Amphibia, Osteichthyes) were of minor importance. Trophic diversity indices differed between years in the Evros Delta. A brief review of the literature shows that, in contrast to what has been previously suggested, trophic diversity of Gull-billed Terns is independent of latitude. Methodological aspects are discussed in order to improve our knowledge of the feeding ecology of Gull-billed Terns.