Less-pretty female house sparrows tend to lower their aim when selecting a mate. Addressing the lack of studies on condition-dependency of female mate choice, researchers writing in the open access journal BMC Evolutionary Biology found that female sparrows of a low quality prefer males of an equally low quality.

Researchers from the Konrad Lorenz Institute for Ethology in Vienna studied sexual selection preferences in the common house sparrow. Though it has always been assumed that females will want to choose the best possible mate, in terms of reproductive and genetic fitness, Matteo Griggio and Herbert Hoi have found that, in fact, unattractive females dare not dream of mating with males who are considered out of their league.

In sparrow terms, males who have a large patch of dark-colored feathers on the chest -- the "bib" or "badge" -- are considered the most attractive. The bigger the badge, the more likely the male is to have the best territory in which to rear offspring, so if females were to believe that size matters, the big-badged males should be irresistible. In order to investigate female preference, the research team randomly divided ninety-six male house sparrows in to two groups -- those with an artificially enlarged black throat patch and those with an average patch. By observing the behavior of 85 different females it was possible to define a 'preferred male' as the male with whom the female spent most of her time.

"Actually, we found that overall, female sparrows don't have a preference for badge size in males," Griggio explains, "but we did find that less attractive females -- those with a low weight and poor condition -- have a clear preference for less attractive males with smaller or average-sized badges." Rather than not find a partner, unattractive females will simply settle for an unattractive male.

Griggio continues: "There is some good news for the plainer females though -- while they may be forced to settle for less dominant males with small chest badges, these males have been shown to invest more time in parental care than their good-looking counterparts."