Female Age and Egg Size in the Lesser Snow Goose

We studied the relationship between female age and egg size of the Lesser Snow Goose Anser caerulescens caerulescens at La Perouse Bay, Manitoba, Canada, over a period of 15 years (1976-90). Two and three years old birds laid significantly lighter eggs than the rest of the population in a given year, laying sequence and clutch size. Analysis of repeated 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 variation was the same in both young and old birds, with younger birds laying slightly smaller eggs in each position within the laying sequence. Some physiological maturation process was probably responsible for the smaller eggs younger birds laid because the pattern held within individuals. However, changes in egg size and shape may be due to breeding experience rather than age itself. We detected no evidence for age-specific differences in egg size of older birds. Thus, neither senescent declines in egg size nor an increased allocation of reserves to reproduction appear to be occurring in this species.