FEMALE AGE AND EGG SIZE IN THE LESSER SNOW GOOSE

We studied the relationship between female age and egg size of the Les ser Snow Goose Anser caerulescens caerulescens at La Perouse Bay, Mani toba, Canada, over a period of 15 years (1976-90). Two and three years old birds laid significantly lighter eggs than the rest of the popula tion in a given year, laying sequence and clutch size. Analysis of rep eated measures of individual birds showed equivalent results. Younger birds also laid eggs which were significantly longer and thinner than eggs laid by older birds. The pattern of intraclutch egg size variatio n was the same in both young and old birds, with younger birds laying slightly smaller eggs in each position within the laying sequence. Som e physiological maturation process was probably responsible for the sm aller eggs younger birds laid because the pattern held within individu als. However, changes in egg size and shape may be due to breeding exp erience rather than age itself. We detected no evidence for age-specif ic differences in egg size of older birds. Thus, neither senescent dec lines in egg size nor an increased allocation of reserves to reproduct ion appear to be occurring in this species.