The diet of Common Gulls Larus canus breeding on the German North Sea coast

The diet of Common Gulls Larus canus was analysed from pellets and faeces during the breeding period in 1995. Three geographically well-separated colonies were selected: one located close to the open North Sea (Amrum Island), one at the inner edge of the Wadden Sea (Nordstrandischmoor Island), and one in the tidal river Elbe (Lühesand Island). The birds fed upon a large variety of food types. In the two colonies adjacent to the sea, prey types from the tidal flats were most numerous (mainly crustaceans, polychaetes, bivalves). Gadids and Smelt Osmerus eperlanus were the fish identified most often, whereas discards from fisheries were relatively important during the early incubation period on Amrum and Nordstrandischmoor. Terrestrial food was also taken (earthworms, insects) but was less important. On Lühesand, in contrast, Common Gulls fed predominantly on terrestrial food (earthworms, insects, mammals and fruits). These birds hardly utilised the river Elbe and associated freshwater tidal flats. The diet changed in all three colonies over the breeding period. The proportion of mammals increased while that of fish and bivalves (only the two colonies close to the coast) decreased. On Lühesand, a considerable proportion of the pellets consisted of cherry stones during the chickrearing period. Common Gulls were relatively widely distributed in the inner German Bight but all major concentrations were located close to land, chiefly in front of the mouths of the rivers Elbe and Weser. Common Gulls (up to 150 individuals) regularly attended the inshore shrimping vessels.