What`s behind the color and pattern of bird feathers?
(PHYSorg.com Biology)

While it may be true, as the old adage goes, that `birds of a feather flock together,` what is less certain is how the feathers on those birds come to have their distinct patterns and colorations. Current data suggest that patterns of stripes and spots on animals` fur or feathers are formed through an open-ended or stochastic process during the embryonic formation of skin, at which time a dynamic-such as Turing`s reaction-diffusion-is at play. On the other hand, owing to their specific orientation and periodictity, and the highly reproducible nature of these patterns within species, it is thought that other factors may also be at work in the development of patterning and coloration.