... phenotypes. Melanins are polymers constituting the most abundant pigments in animals, and the sulphurated form (pheomelanin) produces colors that are similar to those produced by psittacofulvins. However, the differential contribution of these pigments to psittaciform phenotypic diversity has not been...

..., if they did so, they would pay greater production costs than high-quality individuals. We tested an alternative explanation for the black bib size of male house sparrows, Passer domesticus , an honest signal of quality the expression of which is negatively related to levels of the pigment pheomelanin...