The evolution of multiple male traits in the yellow-browed leaf warbler

I examined how male competition and female choice influence the evolution of multiple male traits in the yellow-browed leaf warbler,Phylloscopus inornatus, by investigating the roles of colour patches, territory size, body weight and song rate in sexual selection. Comparison of 3 years of observational studies and 3 years of experimental studies, in which the colour patches on the wings of males were experimentally altered, suggest several mechanisms that may explain the evolution of multiple characters in males. First, females based their choice of mates on several male characters, not a single character. Second, the male characters preferred by females were different in observational and experimental studies. Females apparently preferred high-quality males as mates, and were able to vary the characters used in mate choice to distinguish these individuals under both experimental and observational conditions. Third, the characters important in male competition differed from those that formed the basis of female choice: the manipulation of colour patch size directly affected male territory size but was not associated with female choice. These results may provide an explanation for the diversity of sexual ornaments shown by males of many species.