Looks Matter (in the Bird World): During a study of reproduction habits of blue tits (Cyanistes caeruleus) researchers found that a few aesthetic traits exhibited by male and female birds act as signals for the opposite sex to learn who has the best genes, who can chose the best nesting site, who can command the best territory and, ultimately, who will be best parent. The visual cue for male blue tits is the quality of the female’s ornamentation — the ultraviolet coloration of her crown. According to the BioMed Central press release, ornamentation also plays a role in competition between males and between females, as well as signaling potential reproductive success. via PhysOrg.com