Nutritional status does not explain the increase of carotenoid-based coloration associated with age in Great Tits Parus major

In many bird species, yearling individuals are less colorful than older ones. However, the causal factors behind this difference of color are for the moment unknown. Here, we used ptilochronology in Great Tits Parus major to assess how nutritional conditions experienced by the same birds as yearling and adult are associated with this increase of coloration. Nutritional status was not different between yearling and adult individuals, suggesting that the increase in coloration with age is not due to an increase in foraging efficiency with age. Instead, our study implicates other behavioral and/or ecophysiological factors that drive yearling/adult differences in carotenoid ornamentation