English

Noun

nictitating membrane

nictitating membrane ‎(plural nictitating membranes)

1. A transparent protective fold of skin acting as an inner eyelid in birds, reptiles and some mammals.
   • 2015, Elizabeth Royte, Vultures Are Revolting. Here’s Why We Need to Save Them., National Geographic (December 2015)

     As the wildebeest shrinks, the circle of sated birds lounging in the short grass expands. With bulging crops, the vultures settle their heads atop folded wings and slide their nictitating membranes shut.

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