Plumage coloration and parental provisioning effort in varied tit (Sittiparus varius)

Plumage coloration, a key morphological trait in birds, is ecologically significant in sexual selection. Plumage coloration not only reflects individual body condition but also influences reproductive investment. In this study, we investigated the influence of plumage coloration in Varied Tits (Sittiparus varius) on the provisioning effort of individuals and their mates during the breeding season (April-July 2021). Our results showed that provisioning effort was associated with mate plumage coloration. Specifically, the proportion of larvae in male provisioning was negatively correlated with female hue (p = 0.048) but positively correlated with female chroma (p = 0.049). In addition, female total food provisioning was positively correlated with male chroma (p = 0.029) and brightness (p = 0.038). These findings suggest that Varied Tits adjust their parental investment based on their mate’s plumage coloration. By contrast, no significant association was found between plumage coloration and individual provisioning effort in either sex. Overall, this study provides novel evidence for the signaling role of plumage coloration in birds and contributes to the evaluation of avian phenotypic traits.