Two pieces of information in a single trait? The yellow breast of the great tit (Parus major) reflects both pigment acquisition and body condition

Carotenoid-based plumage coloration has been shown to be dependent both on pigment content and feather structure. Against this background, we predict a relationship between feather pigment content and plumage hue. Furthermore, given the susceptibility of chroma to developmental perturbation of feather structure, we predict body condition to be related to chroma. We tested these predictions in the great tit, Parus major. Carotenoid content in yellow breast feathers was analysed by high-performance liquid chromatography (HPLC). Lutein was the main carotenoid contained in great tit feathers, followed by zeaxanthin. The hue of the feathers was accurately predicted from their lutein concentration, and chroma was predicted from the body condition value. Our data suggest that plumage coloration in the great tit could independently provide information on the ability of the signaller to collect carotenoids (via hue) and body condition (via chroma). Published results both from the great tit and other species support this view.