Complex plumage patterns can be produced only with the contribution of melanins

Abstract

Birds exhibit an extraordinary diversity of plumage pigmentation patterns. It has been overlooked, however, that complex patterns can be produced only with the contribution of melanins because these are the only pigments under direct cellular control. We tested this hypothesis for the first time examining the plumage patterning of all species of extant birds. Thirty-two percent of species show complex plumage patterns, the vast majority (98%) including the contribution of colors produced by melanins. Only 53 species show complex patterns that do not contain melanin-based colors, and these species display unusual colorations and belong to three families where innovative metabolic modifications of conventional carotenoid pigments have been described. While the adaptive functions of complex plumage patterns remain poorly understood and in most cases are ascribed to fulfill camouflage, our findings indicate that such functions will be understood only by considering the synthesis pathway of melanins.