Bright Blue Tits Make Better Mothers Than Duller Birds

It turns out that the brighter you are, the better you are at being a mother--assuming that you're a blue tit, of course. Scientists have discovered that female blue tits with brightly colored crowns are better at being moms than duller birds.

Birds have a unique sense of sight. Unlike humans, they can see ultra-violet (UV) light. This means that while a blue tit just looks blue to us, another bird sees the added dimension of appearing UV-reflectant. In order to see how this might impact how well a bird does in the wild, the scientists conducted a three-year study of blue tits.

The scientists examined mother blue tits in addition to their offspring, watching just how many eggs the females laid and how successful they were at bringing up their brood. In the end, the researchers found that mothers with more UV-reflectant crown feathers did not lay more eggs. However, they did fledge more offspring than their duller counterparts. In addition, these brightly colored 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," said Kathryn Arnold of the University of York in a news release. "Our work shows that this is a wise choice. UV plumage can signal maternal quality in blue tits, so a male choosing a brightly colored female will gain a good mother for his chicks and a less stressed partner."

The scientists aren't exactly sure why more brightly colored females are less stressed or more successful. Yet it's clear that the dowdy blue tits are generally worse off as mothers.

"With up to 14 chicks to care for, blue tit mothers in our study were feeding their broods every couple of minutes," said Arnold. "We showed that dowdy colored females found this level of hard work twice as stressful compared with brighter mothers. Also, the mothers with more UV-reflectant crowns were highly successful, fledging up to eight more chicks than females with drabber feathers."

The findings are published in the journal Behavioral Ecology.