Why birds’ eyes can be blue, green, pink or orange

Whereas birds typically have vibrant plumage, the dazzling variety within the color of their eyes is perhaps simply as necessary for his or her survival and reproductive success, in accordance with a review of hundreds of studies on the subject.

Many birds have brightly coloured eyes. The black-and-red-broadbill (Cymbirhynchus macrorhynchos), for example, has sapphire blue or vivid emerald eyes. The Satin bowerbird (Ptilonorhynchus violaceus) has irises of periwinkle and purple. Some species of inexperienced pigeon (within the genus Treron) have magenta peepers …