I knew that the blue color of most birds is not a pigment but rather due to feather structure, and that the iridescence of hummingbird gorgets and some other iridescent bird colors is also non-pigment related, but just how this works was hard to wrap my brain around. I just stumbled onto a nice, short article on the Cornell site that reviews these different ways birds have color. Enjoy:
A very colorful article, and they offered an incredible photo montage free as desktop wallpaper for computer and mobile devices, which I’ve taken advantage of! Thanks!