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.
"Previous studies have shown that male blue tits prefer mates that exhibit highly UV-reflectant crown feathers. Our work shows that this is a wise choice. UV plumage can signal maternal quality in blue tits, so a male choosing a brightly coloured female will gain a good mother for his chicks and a less stressed partner," author Dr Kathryn Arnold, from the University of York's Environment Department, said.
The study is published in the journal Behavioral Ecology.
--ANI (Posted on 14-08-2013)