Anatomy: Nictitating Membrane

This great horned owl is winking sideways! He’s closing his nictitating membrane. The nictitating membrane, or third eyelid, is named for the Latin word “to blink” (nictare).   Its function is to protect and moisten the eye while allowing the animal to see.  Sometimes the membrane is transparent, sometimes translucent.  It depends upon the species. Birds, … Continue reading Anatomy: Nictitating Membrane