Age-dependent association between testosterone and crown UV coloration in male blue tits (Parus caeruleus)

Anne Peters, Kaspar Delhey, W Goymann, Bart Kempenaers

Research output: Contribution to journalArticleResearchpeer-review

47 Citations (Scopus)

Abstract

The proximate basis of sexual traits can suggest mechanisms maintaining honesty in signalling. A central role hereby has been attributed to testosterone, although its importance for brightly coloured plumage has been questioned. We determined circulating testosterone levels in male blue tits captured at the start of breeding and demonstrated an age-dependent relationship between testosterone and male crown UV/blue coloration. In yearling males, testosterone increases with increasing ornamentation (higher UV chroma, higher chroma, more UV-shifted hue), whereas in older males, this relationship is negative, with less UV-ornamented males having higher testosterone. This pattern is robust since it occurred in 2 years, before and after egg laying, and in males sampled during the day and during the night, despite a tenfold difference in testosterone levels. Since more UV-ornamented young males gain higher within-pair paternity, while less UV-ornamented older males achieve more extra-pair matings, the results imply that higher testosterone is associated with reproductive success and attractiveness in both age classes. We hypothesise that this relationship could result from causal effects of testosterone on coloration or through associations with behaviour and suggest ways to test these hypotheses. Our results caution against premature dismissal of a potential role for testosterone in maintaining honesty of plumage signals
Original languageEnglish
Pages (from-to)666 - 673
Number of pages8
JournalBehavioral Ecology and Sociobiology
Volume59
Issue number5
DOIs
Publication statusPublished - 2006
Externally publishedYes

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