Plumage ornaments
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The balck throat patch (bib) of male house sparrows
is one of the best studied avian plumage patterns. Both our studies
and other investigations showed that the size of the bib predicts the
individuals' dominance rank. However, beside the status-signalling bib,
male sparrows possess several other conspicous plumage ornaments.
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Among these ornaments, one of the most conspicuous
is the white wingbar that males often display upon aggressive encounters.
In laboratory and field studies we investigated how these plumage ornaments
may influence the birds' social and aggressive behaviour. Our lab observations
showed that male sparrows use their conspicuous wingbars to deter their
aggressors in encounters during foraging.
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Conspicuous ornaments are often thought to attract predators such as raptors and thus may be costly to maintain. In a field experiment we tested whether more ornamented sparrows show a stronger response to increased predation risk. Interestingly, we found no evidence that the black bib and the light wingbar of sparrows had such predation costs. (Publication in preparation.) We also study the relationship of these ornaments with the breeding performance and health status (papilloma viral infections) of individuals in a free-living sparrow population since 2004. |
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