Iridescent feathers, like those found on hummingbirds and peacocks, create color through structural coloration. These feathers contain microscopic layers of keratin and air bubbles that create an effect called thin-film interference.
When light hits these structures, it bounces between the layers and certain wavelengths are amplified while others are cancelled out. This creates colors that appear to shift and change depending on the viewing angle. The exact color seen depends on:
- The spacing between structural layers
- The viewing angle
- The intensity and angle of light
This explains why a hummingbird’s gorget (throat patch) can appear brilliant red from one angle and dark from another.