Effects of Sea-surface Temperature on Egg Size and Clutch Size in the Glaucous-winged Gull

Abstract

Abstract. The hypothesis that the egg production capacity of northeast Pacific seabirds is reduced in years with higher spring sea-surface temperatures was tested with data collected on Glaucous-winged Gulls breeding on Triangle Island, British Columbia, Canada, from 2002 to 2011. The mean clutch size varied from 2.3 to 2.9 eggs nest-1, but contrary to prediction, there was little relationship between clutch size and ocean temperature. In contrast, the mean egg size increased with temperature (opposite to the predicted decrease), but that effect was modest in size and limited to clutches of one and three eggs. The within-clutch variation in egg size differed little from year to year, and was unrelated to temperature. The results suggest that higher sea-surface temperatures do not compromise egg production in Glaucous-winged Gulls, a situation unlike that for some other species of marine birds on Triangle Island Received 6 December 2011, accepted 18 February 2012.