A WHAT Eyelid?!

The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent eyelid that can be drawn across the eye to clean it, for protection and to moisten it while maintaining visibility and staying vigilant and aware of potential threats.

It slides horizontally across the eye approximately every 3-4 seconds – unless the crane is probing underwater, which they often do. As they use their long bills to probe for fish, frogs, snails and blue crab, the nictitating membrane remains over the eye, protecting it from sticks or other objects, all the while allowing them to see through the transparent eyelid.

Take a look at the photos below to see the nictitating membrane of Whooping crane number 4-12 in the open and closed position. CLICK the image to enlarge.

nictitating membrane, whooping crane

The image on the left is 4-12 with the nictitating membrane open. On the right the membrane is still covering his eye. Notice the drop of water on his bill? He’s likely just come up for air and hasn’t yet opened the membrane.

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  1. Margie Tomlinson February 18, 2015 8:52 pm

    Thank you, Heather! This is great, interesting info., and what a handsome bird this one is!

  2. Bikebrains February 18, 2015 3:00 pm

    “As they use their long bills to probe for fish, frogs, snails and blue crab,”. On the subject of blue crabs, were the colts ever treated to a Welcome-to-St.-Marks bucket of blue crabs?

  3. Patti February 18, 2015 6:14 am

    Now that’s a cool feature! Have heard it but yet to see it! great photos…:)