FORAGING ECOLOGY OF FOUR GULL SPECIES AT A COASTAL-URBAN INTERFACE

Coastal urban environments provide a potentially diverse source of food for gulls, including items of marine, terrestrial, and anthropogenic origin. Our objective was to examine variation in the diet and use of feeding habitat of four species of gulls, the Laughing (Leucophaeus atricilla), Herring (Larus argentatus), Great Black-backed (L. marinus), and Ring-billed (L. delawarensis), at a coastal urban interface. We necropsied, identified the sex and age class, and quantified the stomach contents of 1053 Laughing, 249 Herring, 67 Great Black-backed, and 31 Ring-billed Gulls collected near the New York City metropolitan area in 2003 and 2004. Great Black-backed Gulls specialized on marine foods, whereas Ring-billed Gulls were generalists. Laughing Gulls and Herring Gulls favored marine foods and foraged in marine habitats but also used terrestrial and anthropogenic food sources. We found evidence that demographics influenced the gulls' choice of diet and use of feeding habitat. Laughing Gulls and Herring Gulls switched their use of feeding habitats at various stages of breeding, exploiting :terrestrial prey and feeding habitats most during chick rearing. Interspecific and intraspecific differences in the four species' diet and use of feeding habitat apparently allow for their coexistence at this coastal-urban interface.