The bigger the eyes, the more the pupils can expand and let light in, which helps them see in the dark. That’s why you see a lot of nocturnal animals with these big eyes. Something crazy about owls and really all birds and reptiles is that the size of their pupil is controlled by skeletal muscle. So what that means is they decide how big they want their pupil. Whereas for us, we don’t have that. We can’t make that decision. That’s all part of our nervous system and it’s all reflective and automatic. Bigger eyes also mean more space between the lens at the front of the eye and the retina at the back. This distance helps the owl’s eyes focus a bigger and more sharp image on their retina, resulting in their impressive vision. For example, the tawny owl can se e about 2 or 3 times better than us humans, but of course vision varies from owl to owl. The other amazing thing about owl eyes is their shape. Usually when referencing eyes we talk about “eyeballs.” But in this case, owls have eye tubes. Scientists believe that as birds evolved, their center of gravity moved to the center of the body to help with balance when flying, so their heads had to become lighter. This is the reason owls have tubular eyes. A tubular eye takes up less space then a round, or globular eye and in turn, weighs less.
