Yellower blue tits make better dads - Biology - research on European bird species - Brief Article

Science News, Feb 16, 2002

Among the little European birds called blue tits, it's the yellow feathers that mark a good dad.

That's the conclusion of a novel experiment by Juan Carlos Senar and his colleagues at the Museu de Zoologia in Barcelona. They've been investigating what information flashy male-bird feathers might reveal to females. Studies in several other birds, such as house finches, have shown that females prefer males with plenty of the orange-yellow carotene pigments in their feathers. Senar wondered whether yellow advertises good genes or behavioral traits that make for good parenting.

Previous work indicated that the yellowness of a male blue tit's breast indicates how many caterpillars he's eaten. To a female, therefore, a particularly yellow male might be the kind of mate that's good at feeding his chicks.

To explore the idea, Senar and his colleagues switched 70 clutches of blue tit eggs from their original nests to foster nests with males sporting breasts of varying yellowness. When the fledglings reached 2 weeks of age, the researchers checked the chicks' growth by measuring the length of a leg bone.

The larger youngsters tended to come from nests with a foster father with unusually yellow feathers, the researchers report in the Feb. 7 Proceedings of the Royal Society of London B. The researchers also found no link between the youngsters' growth and the color of the original dad's feathers, indicating that the yellowness of feathers may not be an indicator of good genes. Together, these findings bolster the connection between good parenting and yellow feathers.

"This is the first paper to be able to separate the genetic and the good-parent component" of what a male offers a female, says Senar. --S.M.