A female Great Horned Owl shows off her nictitating membrane, a third eyelid, which moves horizontally across the eye. This membrane is actually a thin translucent fold of skin that helps birds keep their eyes moist, protected, and clean. Video courtesy of Cornell Lab Bird Cams.

A female Great Horned Owl shows off her nictitating membrane, a third eyelid, which moves horizontally across the eye. This membrane is actually a thin translucent fold of skin that helps birds keep their eyes moist, protected, and clean. Video courtesy of Cornell Lab Bird Cams.

/r/Ornithology: Ornithology - Welcome to Ornithology, a subreddit dedicated to the scientific study of wild birds. This is a place to discuss wild birds in a scientific context — their biology, ecology, evolution, behavior, and more. - September 1, 2021 - 12:55