Great Horned Owls’ eyes work the same as yours and mine. They have to have light to see and too much light hurts their eyes. Because their eyes are so large they have a different type of muscle that controls the amount of light getting in. We have a smooth muscle that automatically adjusts pupil size to different levels of light. If you go into a darkened room, in a few minutes you will be able to see things more clearly as your pupils get larger and allow more light..
An owl’s eyes can adjust as quickly as you can snap your fingers. They have a striated muscle for their eyes that controls pupil size and focusing ability. Not only can they see better in changing light (ie. sunrise and sunset ) but they can see clearly more quickly as well.
If you had Great Horned Owl eyes in your head, they would be the size of grapefruits!
Owls’ eyes can’t move in their heads. They can’t move their eyes back and forth and up and down without moving their whole heads as well. This can give them a mechanical or battery-powered look.
Looking straight ahead, an owl can move his head 180 degrees in either direction – they can’t move their heads around and around and around…..
Owls have a valve system in their necks that allows blood to flow to their brain even though their neck is twisted backwards. Think of what happens to a garden hose when you twist it.
Owls can see three times farther than you or I. A hawk floating in the sky can be seen 3 kilometers away by us. An owl can see one 9 kilometers away.
Owls don’t see color very well but even with that disadvantage, they are not being fooled by colorful camouflage.
Not all owls are visual hunters. You can guess whether an owl is using its eyes or ears by looking at its face; if the ears are large, that is most likely what is primarily used to hunt, likewise with the eyes. Owls such as a Great Horned or Snowy use their ears (auditory) to hunt.
There is only one type of brown-eyed owl in Alberta and that is the Barred owl. There is no real well-understood reason for this, however all brown-eyed owls are nocturnal.
Owls can constrict and dilate their pupils at will. They can do them individually as well, constricting one and dilating the other at the same time.
Owls have three eyelids for each eye, a top one, a bottom one and one that comes from the side. The third eyelid is called a nictitating membrane; cats, dogs, deer and many other animals have them as well. When an owl blinks, it blinks from the top down and from the side across. When an owl is sleeping it brings its bottom eyelid up.
Studies have shown that an owl can go to sleep with one half of its brain while the other side is awake, so an owl can literally sleep with one eye open!