Prettier Great Tits Have Healthier Babies: Female Birds Show off Vibrant Patterns

With its black stripe across its chest and the white patches on its cheeks, a female great tit is striking in its appearance. Yet these same markings could reveal how well her offspring are able to survive. It turns out that prettier birds have healthier babies, according to a new study.

The researchers used two mothers with different patterning in order to test their theory. They then swapped the birds' chicks and examined how well the offspring did with their new mothers. The researchers noted the patterning of the mothers, and also compared the chicks' weight, size and immune strength over several weeks.

It turned out that there was indeed a correlation between patterning and how well the offspring did. Researchers found that offspring who had a genetic mother with a larger black breast stripe gained more weight over the first two weeks. The immaculateness of both genetic and foster mothers' white cheek patches, in contrast, was related to the strength of the chicks' immune responses. This suggested that this was due to both nurture and genetics.

Great tits are monogamous, mating with only one individual. While male great tits are similarly brightly colored, though, researchers could find no relation between the male coloration and the health of the baby birds.

The connection reveals how these birds may have evolved their patterning in order to signal reproductive fitness.

"Bigger, healthier babies are important to the reproductive success of individuals because they are more likely to survive to adulthood--so it is useful for birds to be able to work out which potential mates will produce the best babies," Vladimir Remes and Beata Matysiokova, researchers involved in the study, said in a press release. "Maintaining bright coloration uses up resources, which could otherwise be invested in reproduction or self-maintenance--consequently, the evolution and maintenance of ornamentation in female great tits is probably due to direct selection by males."

The research was published in the journal Frontiers in Zoology.