March 25, 2013
Healthier Babies From Better Looking Birds
A female great tits' (Parus major) appearance is shown to signal healthy attributes in offspring in a paper in BioMed Central's open access journal Frontiers in Zoology. The black stripe across her breast and white patches on her cheeks correlate to a chick's weight at two weeks and immune strength respectively — though the former seems to signal a genetic benefit and the latter can affect an 'adopted' chick's health, suggesting nurture is involved.
The immaculateness of both genetic and foster mother's white cheek patch was related to the strength of chick's immune response suggesting that this was due to both nurture and genetics. In contrast the body size of a chick was related only to the body size of its genetic mother and not to ornamentation at all.
In these socially monogamous birds both the males and females are brightly colored, however neither the cheek patch nor the stripe in males affected the health of the babies.
Talking about how the ornaments can have evolved to signal reproductive fitness, VladimÃr RemeÅ¡ and Beata MatysiokovÃ¡ who performed this study explained, "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. Maintaining bright colouration 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."