DIET OF RING-BILLED GULL CHICKS IN URBAN AND NONURBAN COLONIES IN QUEBEC

In 1992-1993, we compared the diet of Ring-billed Gull (Larus delaware nsis) chicks reared in urban and non-urban colonies that made up 46% o f the total breeding population of the Quebec portion of the St. Lawre nce River. We analyzed the contents of 877 boli regurgitated by chicks and determined the importance of each food item based on percent volu me. The main items in the chicks' diet were, in decreasing order of im portance, garbage, arthropods, earthworms, fish, and small mammals. Ho use refuse made up the bulk of garbage in the diet of urban gulls, whe reas refuse from nearby poultry farms was important in the diet of non -urban gulls. Chicks more than eight days old consumed more refuse and earthworms and fewer arthropods than younger chicks. A comparison of the chicks' diet in the same colony in 1978 and 1993 showed that the p roportions of refuse and earthworms rose while arthropods and fish dec reased in recent years. These dietary differences may reflect the rece nt changes made to waste management practices and increasing urbanizat ion. Contrary to what many hunters believe, we found no evidence to su ggest that Ring-billed Gulls preyed upon dabbling duck eggs or young.