Male chicks are more costly to rear than females in a monogamous seabird, the Common Murre |
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Authors: | Cameron-MacMillan Maureen L; Walsh Carolyn J; Wilhelm Sabina I; Storey Anne E |
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Institution: | a Cognitive and Behavioural Ecology Programme, Memorial University of Newfoundland, St John's, Newfoundland, Canada A1B 3X9
b Department of Psychology, Memorial University of Newfoundland, St John's, Newfoundland, Canada A1B 3X9 |
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Abstract: | Feeding rates and mass loss during chick rearing were comparedfor individually marked parents of male and female Common Murre(Uria aalge) chicks at Great Island, Newfoundland, Canada, from19972001. Both parents in this socially monogamous seabirdspecies share parental care duties until colony departure, afterwhich the single chick is fed only by its father. Because murresprovision their single chicks with one clearly visible fishper trip, it is possible to accurately determine whether parentsdifferentially feed male and female chicks. Based on slightlygreater mass of males in adulthood, possibly favored by sexdifferences in breeding roles, we predicted that male nestlingswould be fed more than females. Fathers' feeding rate to sons,but not daughters, increased with chick age, whereas maternalfeeding rate increased with chick age for both sexes. When year-correctedfeeding rates of pairs rearing both sexes were compared, bothmothers and fathers fed their sons significantly more than theirdaughters in the later part of the chick-rearing period. Moreover,parents rearing male chicks lost mass at a significantly higherrate than those rearing females. There was no difference infledging age for sons and daughters. These results indicatethat differential parental allocation occurs and has measurablecosts even in a species with only slight adult sexual dimorphism. |
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Keywords: | Common Murre feeding rate parental care sex differences sexual size dimorphism Uria aalge |
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