The signalling function of plumage colour traits in the Chestnut Thrush (Turdus rubrocanus)

Melanin is a common pigment in birds, and several studies have shown that melanin-based plumage coloration could signal individual body condition, social status and personality traits. However, most of these studies have focused on males, and little is known about the role of plumage coloration in females. Here, we investigated whether body condition and personality traits (activity and exploratory behaviour) were associated with plumage coloration in wild populations of the Chestnut Thrush Turdus rubrocanus, an apparently monochromatic species. We also tested whether the signals of plumage colour traits differed between sexes. In this study, we found that females had better body condition compared with males. Females with lower chroma and brightness of their black wings had better body condition, but no plumage colour measures reflected male body condition. Males with a lower red chroma of their brown back plumage were less active, and females with lower red chroma of the back plumage were more active. However, plumage coloration did not explain variation in exploratory behaviour. Our findings suggest that plumage colour traits may act as sex-specific signals in Chestnut Thrushes and these traits may play important roles in sexual or conspecific communication in the wild.