Correlation between plumage coloration and breeding investment in Varied Tit (Sittiparus varius)

Background Plumage coloration, a key morphological characteristic of birds, has ecological significance in the process of sexual selection. It has been found that plumage coloration not only indicates individual body condition but also impacts their breeding investment. Methods In this study, we explored the effect of plumage coloration of Varied Tits ( Sittiparus varius ) on the individual itself and its mate's investment in the breeding season of 2021 (April to July). Results This study demonstrated that, the reproductive investment was found to be associated with the mate’s plumage coloration. Specifically, the proportion of larvae in male provisioning was negatively correlated with female plumage hue (p = 0.048) while positively correlated with female plumage chroma (p = 0.049). Additionally, female total provisioning rate was positively correlated with male plumage chroma (p = 0.029) and brightness (p = 0.038). These findings indicate that Varied Tits adjust their parental investment based on their mate's plumage coloration. By contrast, no significant relationship was found between plumage coloration and self-reproductive investment for either males or females. This study provides novel scientific evidence supporting the role of plumage coloration in birds and offers a new perspective for evaluating avian physical parameters.