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Differences in parental food allocation rules : evidence for sexual conflict in the blue tit?

Research output: Contribution to journalJournal article

Published

Journal publication date07/2007
JournalBehavioral Ecology
Journal number4
Volume18
Number of pages6
Pages674-679
Original languageEnglish

Abstract

Evolutionary conflicts of interest between family members are expected to influence patterns of parental investment. In altricial birds, despite providing the same kind of parental care, patterns of investment in different offspring can differ between parents, a situation termed parentally biased favoritism. Previous explanations for parentally biased favoritism have received mixed theoretical and empirical support. Here, we test the prediction that in blue tits, Cyanistes caeruleus, females bias their food allocation rules to favor the smallest offspring during the nestling stage. By doing so, females could increase the subsequent amount of paternal care supplied by their partner during the fledging period, as a previous study showed that males feed the largest fledglings. When size differences within the brood are less pronounced, all offspring will require similar amounts of postfledging care, and thus, the male parent will lose the advantage of caring for the largest offspring that are closest to independence. In this study, we controlled the hunger of the smallest and largest nestlings in the brood and compared the food allocation rules of the 2 parents. We found that the male parent had a stronger preference than the female to feed the closest nestlings and made no distinction between nestlings based on size, whereas the female provisioned small hungry nestlings more when they were at intermediate distances from her. These differences in parental food allocation rules are consistent with predictions based on sexual conflict over postfledging parental investment.