The Eyes Have It

I yet again wandered many paths in GoogleLand as I researched this female Anna's hummingbird's blink -- so many interesting paths available, and of course I wanted to see them all!

Confirming my initial guess when I saw this image, hummingbirds have nictitating membranes, sometimes called "the third eyelid". The membrane draws "across the eye to protect and moisturize it, while retaining visibility," according to The Ark in Space. "Nictitating" comes from the Latin nictare, to blink.

Many birds have nictitating membranes, including woodpeckers and raptors, which unconsciously activate this built-in eye protection when drilling in trees (woodpeckers) and feeding their young (raptors).

On another website, the hummingbird's nictitating membranes were said to "act like natural flight goggles, protecting the hummingbird's eyes as the little bird zooms through the air." As they can "reach speeds of up to 30 miles per hour while flying and 60 miles per hour while diving," flight goggles seem like a very good idea! 

(The extra shows the same female with her eyes wide open.)

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