Parrot Pigments Preserve Pretty Plumage

Parrot feather pigments appear to have properties that promote resistance to bacterial degradation, reports a group led by Edward H. Burtt Jr. of Ohio Wesleyan University (Biol. Lett., DOI: 10.1098/rsbl.2010.0716). Most birds get their feather coloring from carotenoids in ingested food, but parrots synthesize their own pigment molecules in the form of polyenal lipochromes called psittacofulvins. Scientists believe that the brilliant parrot colors arise from either supramolecular or covalent interactions of the psittacofulvins with structural proteins in feathers, with shorter chain psittacofulvins producing yellow colors and longer chains producing red. Green feathers arise from a combination of a psittacofulvin and melanin, and blue and black feathers come from melanin alone. Previous work comparing black and white feathers indicated that melanin helps feathers resist bacterial degradation. In the new study, Burtt and colleagues investigated the full rainbow of feather colors and found that white and yellow feathers degraded faster than feathers of other colors. The researchers suggest that the pigments may help thicken the cortex of feather barbs, making it tougher for bacteria to break through, or that pigments’ binding to structural proteins makes it more difficult for enzymes to degrade the proteins.