Female blue tits with brightly coloured crowns are better mothers than duller birds, according to a new study led by the University of York.
Unlike humans, birds can see ultra-violet (UV) light. While the crown of a blue tit looks just blue to us, to another bird it has the added dimension of appearing UV-reflectant.
The three-year study of blue tits, which also involved researchers from the University of California Davis, USA and the University of Glasgow, showed that mothers with more UV-reflectant crown feathers did not lay more eggs, but did fledge more offspring than duller females. These brightly coloured mothers also experienced relatively lower levels of stress hormones during arduous periods of chick rearing.
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