UC Irvine

A three year study of Herring Gull (Larus argentatus) reproductive success on four islands in Maine indicated that production of young was controlled by different factors operating on the eggs and chicks. Hatching success was inversely related to the disturbance of colonies by picnickers, which apparently caused the adults to leave their eggs exposed to sufficient solar radiation to addle the eggs. The survival of chicks was lower on islands distant from sources of edible refuse (outer islands) than on islands close to sources of waste (inner islands), regardless of visits by picnickers. The nutrition and growth rates of chicks on inner and outer islands were similar. The attendance of parents on the territories was found to be less on an outer island than on an inner island. It is concluded that differences in parental behavior associated with greater foraging effort were responsible for a higher loss of chicks to predation on the outer islands.