Iturria: NY Times

Observatory

For These Flashy Males, No Modest Mate Will Do

By NICHOLAS BAKALAR

Published: July 9, 2012

Everyone knows that male birds are usually the ones with pretty colors, and that dull-looking females look for flashy mates. But male blue tits, apparently, judge females by their looks. And new research suggests that the males are more attentive fathers to their babies if the mother is pretty.

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Chris Gash

Birds of the species, both male and female, have shiny blue feathers on their heads that reflect ultraviolet light. For the study, published online in the journal Frontiers in Zoology, scientists captured females while they were taking care of chicks and assigned them to either an experimental group or a control group, smearing the crests of the first group with UV-blocking chemicals to make the feathers look dull. Then they restored the birds to their nests.

The male birds made significantly fewer feeding excursions for the nestlings of females with the UV-blocking chemicals on their feathers. The reason, the authors say, is that males judged females with poor coloration less likely to produce healthy offspring, and therefore less worthy of energy expended taking care them — what the researchers call the differential allocation hypothesis.

Providing food is costly, and males do not waste their effort on babies unlikely to reproduce their genes.

“Everyone has focused on male ornaments,” said an author of the study, Matteo Griggio, a postdoctoral researcher at the University of Veterinary Medicine in Vienna. “But in this case, we focused on the females, and found that the males, the fathers, change their behavior according to the females’ appearance. This is one of the first studies to do that.”