EXPLANATION OF EGG-WEIGHT VARIATION IN LESSER SNOW GOOSE

Lesser snow goose (Chen caerulescens) eggs were weighed at the McConnell River, Northwest Territories [Canada], in 1972 and 1973. Mean egg weight was the same in different size clutches. Within each clutch size there was great variability in egg weights; the lightest eggs weighed only 60% as much as the heaviest. This variation was greater than that reported for other waterfowl species. The egg-weight variation resulted in overlap between the weight of the heaviest clutches of a particular size and the lightest clutches of the next larger size. The nutrient commitment to a particular clutch size was not the same for all females. A hypothesis is presented to explain the constancy of mean egg weight among clutch sizes and the great variation in egg weights within each clutch size. It is assumed that there is a heritable component in egg weight of the lesser snow goose and that heavier eggs enhance gosling survival under energetically poor conditions. The mean egg weight is probably adapted to the average environmental conditions at hatch; a wide range of egg-weight genotypes probably survives because of the great annual variation in environmental conditions at hatch.