Age-dependent modulation of songbird summer feather molt by temporal and functional constraints

Yosef Kiat, Nir Sapir

Research output: Contribution to journalArticlepeer-review


Time constraints influence various ecological, lifehistory, and demographic properties of individuals and populations of many species throughout the annual cycle. Feather molt is a timely undertaking that is considered among the three most energydemanding processes in the life cycle of birds. To deal with time pressure, passerines may shorten their molt duration, using three non-mutually exclusive mechanisms: (1) replacing only part of the plumage, (2) increasing the speed of molt, and (3) postponing the renewal of some or all the plumage to a later season (i.e., from the summer to the overwintering period).We used a comparative approach by measuring 12,349 individuals from 134 passerine species to explore how feather molt of juvenile and adult passerines is evolutionarily modulated under time constraints. The results indicate that breeding at northern latitudes and long-distance migration limit the time available for molt and that the consequences of time constraints were age dependent. While the duration of adult summer molt decreased, the extent, rather than the duration, of juvenile molt declined under time constraints. This study highlights the importance of considering time constraints in order to enhance the understanding of selective forces that shape life-history processes and their consequences throughout the annual routine.

Original languageEnglish
Pages (from-to)184-195
Number of pages12
JournalAmerican Naturalist
Issue number2
StatePublished - Feb 2017

Bibliographical note

Publisher Copyright:
© 2016 by The University of Chicago.


  • Annual routine
  • Bird migration
  • Breeding distribution
  • Passerines
  • Time constraints
  • Wing feathers

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics


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