Let me look into your eyes…

Eye color in birds is rich and varied, spanning a range from white to yellow to orange, deep red, brown and black iris color.  The color of the iris might change seasonally, as it does in Brown Pelicans and Double-crested Cormorants (see below);

brown-pelican

White head and neck feathers are part of the breeding plumage of Brown Pelicans, whose eye color also changes from brown to blue during breeding.  Photo taken in New Orleans, February 2013.

or might vary with age, as it does in various raptor species from pale yellow in juveniles to dark brown in adults;

Red-tailed hawk eyes-PentaxForums.com

The amber color of this Red-tailed Hawk’s iris will darken to deep brown as the bird ages.  Photo from Pentaxforums.com

or it might be associated with other flamboyant colors of males advertising their sexual prowess, like the bright red eyes of the Wood Duck,

wood-duck-male-Backyard Biology

Once they molt their full adult plumage, male Wood Ducks retain their bright red eye color permanently.  Photo taken Fall, 2013 on Lake Vadnais.

or the deep golden-orange eyes of the Glossy Starling seen in South Africa a month ago.

The bright orange-yellow eye of this  Starling from South Africa is one of its key identifcation characters.

The bright orange-yellow eye of this brilliant blue-purple feathered Starling taken in South Africa is one of its key identifcation characters. 

With such a diversity of eye color, within a species or over the bird’s lifetime, it seems strange that birds seem to lack the green and blue-hued eyes that are common in other animals, and especially in humans.  A couple of the very few examples of green/blue eyes in birds:

double-crested cormorant

The bright blue iris color indicates breeding condition in Double Crested Cormorants.  Photo taken in New Orleans, February, 2013.

brown_pelican4_bill_stripling-national audubon-

Are blue eyes considered sexy in birds?  Brown Pelicans also sport blue eyes during the breeding season.  Photo by Bill Stripling – National Audubon

Green-eyed birds are either really rare, or rarely photographed; I found only one image of a bird with this rare iris color — a Great Cormorant. (Note:  there are other images of green-eyed birds posted on Google, but some definitely look photo-shopped — see below.)

great cormorant

This might just be a trick of the lighting, but this Great Cormorant’s iris does appear to be green, or at least blue-green.  Photo from sight-touch.com

I didn’t realize until I was looking for more information about “green eyes” that they are rather rare in the human population as well.  Only 1-2% of humans have truly green eyes (not hazel with flecks of green).  That makes my paternal grandmother, me, my daughter, and my grandson rare!  Hmm…that doesn’t sound too rare.

Green color, being a combination of yellow and blue, requires a yellow pigment and a refractive property that reflects blue light (because there are rarely blue pigments that produce color).  In humans, amber and green eye color is produced by a yellow pigment called lipochrome.  Varying amounts of lipochrome and melanin present in the iris generate a host of eye colors varying from yellow-brown to deep, intense grade shades.  Click here to read a fascinating discussion of the derivation of eye color on a blog devoted entirely to that subject.

green-eyed owl

Are you for real?
Or is this a hypnotist’s trick to make you “look into my eyes”?

8 thoughts on “Let me look into your eyes…

  1. Pingback: “Eye” wonder | Back Yard Biology

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