Unusually low success of Herring Gulls Larus argentatus breeding on the North Shore of the Gulf of St. Lawrence, Quebec, Canada

Herring Gulls Larus argentatus are the most numerous species of seabird in the Mingan Archipelago National Park Reserve (MANPR), however little is known about their nesting ecology or reproductive success. The number of active nests, nest density, clutch size, fate of eggs, number of successful nests, hatching success, and mean and median nest hatching dates were recorded in two study polygons on Île Nue, an island in the MANPR, 1994-1996. Clutch size was lower and mean hatching date was later on Île Nue than for typical Herring Gull colonies in all three years of the study. Hatching success was extremely low in 1995. In response, polygons with varying degrees of disturbance were set up to determine the effects of researcher disturbance and a clutch removal experiment was set up to determine whether there were sufficient food sources to allow gulls to produce replacement clutches. Low clutch size and hatching success could not be explained by researcher disturbance, predation, or competition for nest sites, leaving food-stress as the most likely explanation for the low reproductive success.