The trade-off between molt andparental care: a sexual conflict in the blue tit?

Erik Svensson, Jan-Åke Nilsen

Research output: Contribution to journalArticlepeer-review


Breeding activities and molt are generally thought to be mutually exclusive in birds since both are energetically costly and are normally separated in time. However, sometimes molt overlaps with breeding to some degree. A trade-off between adult somatic maintenance functions (feather renewal) and parental care is then to be expected. The consequences of this are largely unknown, and there are few studies that have shown any fitness costs of molt-breeding overlap. We investigated the consequences of molt-breeding overlap by removing first clutches of blue tit Parus caeruleus pairs, thereby inducing late repeat clutches. Among the delayed pairs, a high proportion of males and some females started their molt already during incubation or nestling feeding. Molting males fed their nestling to a lesser extent than non-molting ones, and nestling mortality increased as a direct result of the early timing of male molt. Furthermore, the ability to raise an experimentally enlarged brood was negatively coupled to the molt stage of the male. Our data thus protide evidence that molt-breeding overlap leads to fitness costs, and we discuss the results within the context of sexual conflict and the implications for optimization of avian reproductive decisions.
Original languageEnglish
Pages (from-to)92-98
JournalBehavioral Ecology
Issue number1
Publication statusPublished - 1997

Subject classification (UKÄ)

  • Biological Sciences

Free keywords

  • brood size
  • feeding frequency life-history trade-offs
  • nestling mortality
  • molt
  • Parus caeruleus
  • Paridae
  • aves (birds)
  • blue tit
  • sexual conflict


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