RAINBOW HEADED - Male Bufflehead Duck sports a colorful head pattern. Iridescent feathers in birds are the result of structural patterns in feathers. As iridescent birds move, nanoscale structures within their feathers’ tiny branch-like filaments — known as barbules — interact with light to amplify certain wavelengths depending on the viewing angle. This iridescence is known as structural coloration, wherein crystal-like nanostructures manipulate light.