When we see a domestic pigeon, we are all(OK almost all) enthralled by its grace and beauty. But more than that we physicists are fascinated by a feat of the domestic pigeon.This feat is having an ornament of seduction around its neck. This ornament,an iridescent ring of feathers around the neck(only for males sorry), is mesmerizing to look at.
The shiny metallic colors changes with the change in our viewing angle. This is a signature of interference and diffraction. The iridescence reflects the underlying micro-structure of the neck feathers. These feathers contain barbules, a tilted lattice of fine threads, making a multilayered structure which can selective certain colors in specific directions as dictated by the wavelengths of those colors and the lattice spacing. This phenomenon as a student of physics must know is what we call as interference(Basically, Waves which encourage or discourage other waves they met to sing aloud or shine bright together depending on their (phase) differences).
Here is a video I captured with my mobile of a captured pigeon during the Independence Day celebration at our college premises. You can see the neck-feather's color changes from green to purple and back depending on the view angle. Isn't that good to look at?