Hummingbird coloration is caused not only by the color pigment, but to a greater extent by the interference of light in the feather tufts.
Such "optical coloration" is inherent in a number of birds, especially tropical birds. The color of their plumage changes when the angle of incidence of light changes, that is, the feathers begin to shimmer when they move.
Such "optical coloration" is inherent in a number of birds, especially tropical birds. The color of their plumage changes when the angle of incidence of light changes, that is, the feathers begin to shimmer when they move.