As humans we place exceptional value in the beauty of an individual’s eyes. Most of us will have heard the saying, “Eyes are the windows to the soul”. But besides the cosmetic value, the color of our eyes provides little other benefit to our lives. I have been wondering if it is the same with birds.
This juvenile White Ibis will need to wait a while until it gets the beautiful blue eyes of the adult below
The most obvious difference between eye color in birds and humans is the fact that in certain species of birds, males and females have radically different eye colors. For example male Saddle-billed Storks have dark brown, almost black eyes, and females have bright yellow eyes.
A male Saddle-billed Stork has dark brown eyes
Similar examples exist amongst North American birds. Female Boat-tailed Grackles and Brewer’s Blackbirds have dark eyes whereas the males have bright pale yellowish/greenish-white eyes.
A brightly colored iris in a bird could signify various things. It could function as a “badge”, distinguishing between different age classes. It could advertise sex during the breeding season. It could even help to differentiate between the sexes year-round. The possibility exists that iris color is helpful to birds that live predominantly in certain light conditions. Or it could simply be that the coloration is caused by the chemical make-up of the eye, with little to know function at all. Whatever the reasons for eye color in birds, it makes for a fascinating macro-study of our favorite avian subjects.
I hope James continues to research and photograph birds plus share his fascinating information with those of us who will probably not experience seeing these colorful creatures ourselves.