Mate change and reproductive success in the Lesser Snow Goose.

The reproductive performance of Lesser Snow Geese (Ansercaerulescens caerulescens) at La Perouse Bay was examined in individuals retaining and in those changing their mate of the previous breeding season. Females retaining their mate had on average a slightly higher clutch size than those which did not. Other measures of reproductive success did not differ significantly between the two groups. The phenomenon of larger clutch size was not detectable in samples of older females. Females breeding for the second time, whether they changed mates or not, had a smaller clutch than did older birds, and clutch size was found to increase with age and/or experience, at least up to the third breeding attempt. We conclude that there is no causative relationship between mate loss and lowered clutch size. Nevertheless, females who breed for the first time are more likely to lose their mates and to have a lower-than-average clutch size as second-time breeders. In addition, first-time breeders were less co-ordinated in nest defence than more experienced birds.