Pigments determine the appearance of organisms. However, pigment production can be associated to physiological constraints as in the case of pheomelanin, the sulphurated form of melanin whose synthesis in melanocytes consumes cysteine and consequently reduces the availability of glutathione (GSH) to exert antioxidant protection. Pheomelanogenesis may thus increase the susceptibility to suffer chronic oxidative stress. The possibility that environmental lability in the expression of genes...

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. This hypothesis was tested for the first time examining the plumage patterning of all species of extant birds. 32 % of species show complex plumage patterns, the vast majority (98 %) including the contribution of colors produced by melanins.

Melanins are the ubiquitous pigments distributed in nature. They are one of the main pigments responsible for colors in living cells. Birds are among the most diverse animals regarding melanin-based coloration, especially in the plumage, although they also pigment bare parts of the integument. This review is devoted to the main characteristics of bird melanins.