Cooper's Hawk (Male) Part 4 of 4

n fact, all birds have one: a transparent fold of skin that sweeps sideways across the eye to clean and moisten the cornea. The membrane’s inner surface is covered with brush-tipped cells that lubricate the cornea’s surface with tears. Some birds, including falcons, have a special gland that produces a thick fluid to moisten the cornea. When a peregrine falcon stoops on its prey, flying at up to 240 miles per hour, the nictitating membrane keeps its eyes from drying out. It can be deployed as a bird flies against the wind, or in rain or snow. It may also protect a raptor’s eyes from the sharp claws or teeth of flailing prey and the sharp beaks of its own nestlings. http://baynature.org/articles/natures-safety-goggles/

Here is a great link and images on eye color vs age and nictitating membrane. http://www.themodernapprentice.com/eyes.htm

Thanks Christy. Whenever I see a Raptor,I remember Emily and U!!

Thanks, Braulio.

BTW ,thanks Jellis.

Concord is usually warm. It was mid afternoon and quite warm. I also saw a green metallic bee which usually comes out only when it is warm. You are probably correct.

Thanks Argy. A small observation ,but an observation none the less.

Thanks for your valuable feed back, Suzanne.

maybe it was occasionally moistening it! My daughter has been complaining of dry eyes.

I am not sure why it appeared.Though I dohave some info on nictitating membrane They also have a third eyelid that slides in from the side and is clear. This is called the nictitating membrane and it protects the bird from injury while going down into long grasses to grab prey. Sharks and camels also have nictitating membranes. Why would camels need it? To keep sand out of their eyes!http://www.smm.org/warnernaturecenter/animals/hawk

Thanks Suzzane. Why does it show up occasionally?