Why are kingfishers wings blue?

The wings of kingfishers are not actually blue. They appear blue due to a phenomenon known as structural coloration. Structural coloration occurs when light interacts with the microscopic structure of a surface, rather than with pigments within the material. In the case of kingfishers, the feathers on their wings are covered in tiny, air-filled cavities that act as a natural diffraction grating. When light hits these cavities, it is scattered and reflected back, creating the appearance of blue.