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Impacts of experimentally increased foraging effort on the family: Offspring sex matters

TitleImpacts of experimentally increased foraging effort on the family: Offspring sex matters
Publication TypeJournal Article
Year of Publication2009
AuthorsHarding, AMA, Kitaysky, AS, Hamer, KC, Hall, ME, Welcker, J, Talbot, SL, Karnovsky, NJ, Gabrielsen, GW, Gremillet, D
JournalAnimal Behavior

We examined how short-term impacts of experimentally increased foraging effort by one parentreverberate around the family in a monomorphic seabird (little auk, Alle alle), and whether these effectsdepend on offspring sex. In many species, more effort is required to rear sons successfully thandaughters. However, undernourishment may have stronger adverse consequences for male offspring,which could result in a lower fitness benefit of additional parental effort when rearing a son. We testedtwo alternative hypotheses concerning the responses of partners to handicapping parents via featherclipping: partners rearing a son are (1) more willing or able to compensate for the reduced contributionof their mate, or (2) less willing or able to compensate, compared to those rearing a daughter. Hypothesis1 predicts that sons will be no more adversely affected than daughters, and the impact on parents will begreater when rearing a son. Hypothesis 2 predicts that sons will be more adversely affected thandaughters, and parents raising a son less affected. Although experimental chicks of both sexes fledged inpoorer condition than controls, sons attained higher mass and more rapid growth than daughters in bothgroups. Clipped parents lost a similar proportion of their initial mass regardless of chick sex, whereaspartners of clipped birds lost more mass when rearing a son. These results support hypothesis 1: impactsof increased foraging effort by one parent were felt by offspring, regardless of their sex, and by thepartners of manipulated birds, particularly when the offspring was male.

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