The effect of body condition on subsequent creche attendance in Common Eiders (Somateria mollissima)

Mawhinney, Kim

Creches are groups containing any number of adult female(s) and duckling(s), two or more of which are parentally unrelated. Several authors have suggested that the body condition of ducks is a determining factor in parental care and that females in poor condition more readily abandon their young. In 1997 and 1998, 285 adult female Common Eiders breeding on Green Island were captured and nasal tagged. Our objective was to examine the relationship between adult female condition, using multiple measures of body size, and subsequent membership in creche. The body was higher than average for females tending a brood and the body condition of abandoning females was lower than average regardless at which point they were captured in the incubation period. "Aunties" are females without young which assist brood-caring females in defending a brood. Females that were in good condition and hatched and lost their own ducklings became aunties; and females that lost their clutch early enough in incubation such that they were in good condition when ducklings in the colony hatched became aunties.