Brood and Crèche Stability in the Common Eider of the St. Lawrence Estuary

[The nature and duration of the parental bond in the Common Eider (Somateria mollissima) of the St. Lawrence estuary was studied using 1400 individually tagged females. Several degrees of broodiness were recognized in birds tending broods and/or crèches. Four behavioural categories (B-, A-, V- and N) based on this variability were substituted in lieu of the vague term "aunts" used in previous literature. Eiders of the St. Lawrence estuary did develop a stable and exclusive parental-type bond with all the ducklings they accompanied. Even groups (crèches) of 15-35 ducklings led by one, or sometimes two B-status females did function as family groups (one B-female and 3-5 ducklings) and displayed great cohesiveness after the ducklings reached a certain age (about one week). The minimum duration of the parental-type bond was estimated at 40 days. Some European workers have suggested that crèching is of greater survival value for adult females than for ducklings, allowing females exhausted by incubation to move rapidly to better feeding grounds. Consequently, the link between any female and a crèche was seen as transitory. These views are rejected on the basis of evidence collected in the present work., The nature and duration of the parental bond in the Common Eider (Somateria mollissima) of the St. Lawrence estuary was studied using 1400 individually tagged females. Several degrees of broodiness were recognized in birds tending broods and/or crèches. Four behavioural categories (B-, A-, V- and N) based on this variability were substituted in lieu of the vague term "aunts" used in previous literature. Eiders of the St. Lawrence estuary did develop a stable and exclusive parental-type bond with all the ducklings they accompanied. Even groups (crèches) of 15-35 ducklings led by one, or sometimes two B-status females did function as family groups (one B-female and 3-5 ducklings) and displayed great cohesiveness after the ducklings reached a certain age (about one week). The minimum duration of the parental-type bond was estimated at 40 days. Some European workers have suggested that crèching is of greater survival value for adult females than for ducklings, allowing females exhausted by incubation to move rapidly to better feeding grounds. Consequently, the link between any female and a crèche was seen as transitory. These views are rejected on the basis of evidence collected in the present work.]

Affiliations: 1: (Département de Biologie, Faculté des Sciences et de Génie, Université Laval, Québec, Qué., Canada