ON THE FUNCTION OF FEMALE ORNAMENTS - MALE BLUETHROATS PREFER COLORFUL FEMALES

Female ornaments in animals with conventional sex roles have tradition ally been considered non-functional, being merely a genetically correl ated response to selection for male ornamentation. Alternatively, fema le ornaments may be influenced by selection acting directly on the fem ales, either through female-female competition or male choice. We test ed the latter hypothesis in mate choice experiments with bluethroats ( Luscinia s. svecica), a passerine bird in which females vary considera bly in coloration of an ornamental throat patch. In outdoor aviaries p laced in prime breeding habitat, males were allowed to choose between a colourful and a drab female. We found that males associated more wit h, and performed more sexual behaviours towards, colourful females. Fe male coloration was not age-related, but correlated significantly with body mass and tarsus length. Thus, we have demonstrated both a male p reference for female ornamentation, and a relationship between ornamen t expression and female body size, which may be indicative of quality. Our results refute the correlated response hypothesis and support the hypothesis that female ornamentation is sexually selected.