Feeding ecology of expansive yellow-legged gull Larus cachinnans insouthern Poland: Habitat utilization, foraging tactics and age relatedefficiency

摘要

The Yellow-legged Gull Larus cachinnans occurred originally in the Mediterranean and Black Sea basins, lately it has become an expansive species in Europe. First breeding in southern Poland was recorded in early 1990s, the population size of this species has risen and northward range expansion has followed. In 2000-01 we studied feeding ecology of Yellow-legged Gulls breeding at the largest inland colony of this species located in sedimentation basin near Tarnow (southern Poland). We found that gulls stored a large number of food items at the nests, what indicates the high quality of feeding conditions in the area. Many more food items were found during the chick-rearing period than during the incubation period. In both periods fish were numerically dominant, but during incubation there was significantly more human refuse at nests, and less of other bird species from the breeding colony. Among fish, Carp Cyprinus carpio was a dominant species. During the prebreeding period most birds foraged on a refuse dump during the chick-rearing period fishponds were the most important foraging grounds. The success of three main foraging tactics was analysed: digging, fishing and kleptoparasitism.