Showy ornaments are considered as outcome of sexual selection processes. They provide a “badge of status” to impress conspecific rivals or potential mating partners. Elaborated ornaments could by themselves be attractive or signal aspects of individual quality, but many species display not only a single, but a set of different ornaments. There are several hypothesis, explaining the existence of multiple ornaments suggesting that different ornaments serve as different information source, providing either additive or redundant information on the same quality aspect, or being simply evolutionary leftovers with no further relevant information. Although, females of many species display elaborated traits, most studies regarding multiple ornaments focus on males. Given, that in many species females do also display multiple ornaments, the question about their functional significance arises.
To understand the existence of female multiple ornaments we investigated ornamental features of female superb fairy wrens (Malurus cyaneus), focusing on song and plumage characteristics. Female fairy wrens do sing complex songs, which they use in territorial defence, but they also have bright blue tail feathers. By examining the relationships between song and plumage colouration characteristics and relating them to fitness parameters we try to determine whether and to what extend existing hypothesis on multiple ornaments in males may be also applicable to females. Based on song recordings and spectrometric measurements including UV-colouration of tail feathers, we derived a series of different song and plumage parameters.
Our results indicate interrelationships between song complexity and UV-colouration as well as green colour aspects in the tail. These results and their relationship to fitness parameters suggest that different traits do provide different information. To our knowledge, this is the first study investigating multiple traits in female songbirds, raising the idea that multiple signalling of sexually selected traits is not restricted to males only.