I found this violet bellied hummingbird (Juliamyia julie) in Panama shortly after it died. The iridescence in hummingbird feathers does not come from pigmentation; it is structural. Microscopic “bubbles” in hummingbird feathers refract light; the size and arrangement of the bubbles determines the colors that escape, creating brilliant patterns like the rainbow seen on this specimen.
[Photo and caption by Alexander Vining]
Osorio, D., & Ham, A. D. (2002). Spectral reflectance and directional properties of structural coloration in bird plumage. Journal of Experimental Biology, 205(14), 2017-2027.