Psittacofulvin

pigments, sometimes called psittacins,[1] are responsible for the bright-red, orange, and yellow colors specific to parrots.

[2] In parrots, psittacofulvins are synthesized by a polyketide synthase enzyme that is expressed in growing feathers.

[5] Colorful feathers with high levels of psittacofulvin resist feather-degrading Bacillus licheniformis better than white ones.

[6] Both carotenoids and psittacofulvins have narrow-band absorbance spectra, reflecting pale yellow or red pigmentary colors, making them difficult to distinguish between using spectral measurements.

Birds have tetrachromatic vision, which means that they have four types of cone cells with peak sensitivities to longwave (l), mediumwave (m), shortwave (s), and ultraviolet (uv) or violet (v) light as well as transparent oil droplets made of carotenoid filters (with mainly the pigments galloxanthin, zeaxanthin, and astaxanthin) that refine spectral sensitivities of the l, m, and s cone-types.