promiscuity’s for the birds

Finally, what adulterous female songbirds have always wanted: Scientific proof of the evolutionary advantages of promiscuity. A team of researchers from the Max Planck Research Center for Ornithology in Germany and the Zoological Museum in Norway spent four years studying a population of songbirds known as blue tits breeding in the Viennese Forest in Austria. A female blue tit normally chooses a single social partner, a male to defend a territory and to help care for offspring, but she also occasionally mates with other males outside her breeding territory without her partner’s knowledge. The researchers report in the Oct. 16 Nature that they have found that the offspring from these extramarital affairs were more genetically varied than those sired by her social mate, and were more likely to survive and reproduce. Females from these extramarital couplings were found to produce larger clutches of eggs and lived longer. Males from these couplings also produced more surviving offspring. As an added bonus, these males also tended to have more elaborate head crests, assumed to make them more attractive to other females. The study supports the idea that females mate many times to get the best possible genes for their young and gives evidence that evolutionarily speaking — at least for female blue tits — promiscuity may be the way to go.

This news brief appeared in the Random Data column of the Boston Globe’s Health/Science section on 10/21/2003.