| Summary: | Many avian species exhibit a transition from biparental to uniparental care, but the reasons for this pattern are largely unknown. We examined the transition from biparental to paternal-only care in a small Arctic seabird, the Dovekie (Alle alle). We monitored colony attendance of males and females throughout the chick-rearing period in 2008–2010, investigating the sex ratio of breeders and following individually marked parents of both sexes in the colony at Magdalenefjorden (northwestern Spitsbergen). To understand reasons for the female's behavior, we also examined the birds' parental efforts and changes in chick body mass. We found that females fed the chicks less than males but provisioned the chick until very late in the chick-rearing period. Brood desertion occurred in 95% of nests and took place 3 days, 2 days, or 1 day prior to fledging (in 24%, 39%, and 69% of nests, respectively), on the 26th day of the chick's life, on average. Chicks experienced body-mass recession beginning, on average, on the 24th day of life (the recession assumed to be related to the female's desertion) and departed the colony, on average, on the 26th day of life. Contrary to other colonies, we did not find a significant bias of sex ratio in the birds provisioning at the end of the nesting period. The results undermine most general hypotheses explaining the causality of brood desertion. In fact, brood desertion in the Dovekie seems to be flexible and to depend on environmental conditions.
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