Effects of Egging on the Reproductive Success of Glaucous-Winged Gulls

The effects of egging on Glaucous-winged Gull colonies in Skidegate Inlet, Queen Charlotte Islands, British Columbia, were investigated. Egging occurred in the four largest of 18 colonies examined. It caused total reproductive failure in one colony, and it had minimal effect on three other colonies. Egging was the highest cause of mortality, followed by that of eggs being washed out of nests by waves during high tide. The clutch size and hatching success of gulls in colonies disturbed by egging was much lower, and egg-laying was significantly later than in colonies that were not disturbed.