The blue tit's song is an inconsistent signal of male condition |
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Authors: | Parker Timothy H; Barr Iain R; Griffith Simon C |
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Institution: | a Edward Grey Institute of Field Ornithology, Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
b Division of Biology, Ackert Hall, Kansas State University, Manhattan, KS 66506, USA
c Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
d School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK
e School of Biological, Earth, and Environmental Sciences, University of New South Wales, Sydney, New South Wales 2052, Australia |
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Abstract: | Sexually selected traits are often hypothesized to signal malecondition or quality, though empirical evidence is mixed, anda number of alternative models of sexual selection do not requirecondition dependence. We examined the relationship between variousmeasures of condition and dawn songs in male blue tits (Cyanistescaeruleus). We detected 6 largely independent measures of variation(i.e., variables) in these songs. None of these variables wererelated to blue tits' ultravioletblue plumage, a demonstratedsexual signal, thus failing to support the redundant signalhypothesis. We found some evidence that the song variables wemeasured signaled male quality. There were correlations betweenbody size and certain song traits, though neither male age normale recapture in the subsequent breeding season (apparent localsurvival) predicted any song variation. We combined our resultswith published effect sizes comparing blue tit song with malequality variables using meta-analysis and found that a few songmeasures are correlates of male quality, though as in our fielddata, neither male age nor survival appeared related to song.Our relatively large sample sizes (>60), combined with ourmeta-analytical integration of 89 effect sizes, make the resultsregarding the signaling value of our measured components ofblue tit song robust. These results demonstrate that 1) onlycertain aspects of signal variation may be condition dependentand 2) even when components of a sexual signal appear correlatedwith condition in some studies, these signal components maybe unrelated or inconsistently related to a variety of conditionindices. |
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Keywords: | condition dependence dawn song meta-analysis Parus caeruleus survival ultraviolet |
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