We all love owl eyes, but did you know they have some very unique features? I’ve posted about their special eyeballs before, but what about eyelids?
All birds have three eyelids – like humans, they have an upper and lower eyelid. Owls are among the only birds that have a larger upper eyelid than lower eyelid. They are the only birds that blink like humans, by dropping their upper eyelids. But when owls sleep, they close their eyes the way other birds do—by raising the lower lids.
Beneath the two outer eyelids birds have a translucent nictitating membrane, sometimes called a “third eyelid.” This membrane sweeps across the cornea from the inside corner of the eye to the outer edge of the eye. It moistens and cleans the cornea, especially in flight. It is also drawn across the eye when there is a chance the eye might be scratched or damaged such as when capturing prey, flying through brush or feeding their young.
In summation, one could say that owls have three eyelids for each eye: one for blinking (upper), one for sleeping (lower), and one for keeping their eyes clean and protected (nictitating).
Copied from Naturally Curious)
That lower eye lid sounds so useful for sleeping. I have trouble falling asleep in rooms that aren’t perfectly dark, to the point that I cover up LEDs from electronic devices with dark tape. To be an owl!
Some of these LEDs are so dang bright these days! The ones on my KVM were so bright even during the daytime I had to cover them up, it was so distracting.