October 1st, 2015
The piercing glare of an owl can raise the hair on the back of one’s neck. Just as remarkable is the bird’s amazing ability to hunt in nearly total darkness. How does it do it?
It’s all in the eyes. Okay, powerful wings and large sharp talons and beaks help a lot, too, but the owl’s eyes are custom-made for night prowling. While other birds of prey, like eagles and hawks, have very acute vision, none share the owl’s unique abilities. Owls owe their nighttime prowess to:
Binocular vision—owl eyes face forwards, unlike most birds, which have eyes on either side of a narrow head. This gives them 70 degrees of binocular vision that allows for full depth perception and more precise positioning of a target. Humans, by the way, have about 110 degrees of binocular vision, but we’re not as good at catching rabbits.
Eye shape—an owl’s eyes are quite large, especially compared to its body. This helps take in more light, but the shape of an owl eye provides a real advantage. Owl eyes are shaped like a tube instead of a ball, and those tubes contains some pretty amazing anatomical adaptations. The tube allows for a large cornea in relation to the rest of the eye, which allows more light to come in.
Inside the eye—the owl’s cornea (outer coating) and pupil (the center opening) are much larger than in most birds, which let in more light. The owl retina, the layer at the back of the tube, has an excess of rod cells, which process movement and changes in light. They don’t have many cone cells, which process color. This means that owls are mostly color-blind. Some owls have an extra layer of light sensitive cells to capture any light that passed by the retina, further enhancing night vision.
For owls, this ability to see at night and superior hunting perception comes at a cost; intelligent. Owls aren’t very smart. Ironically, the ancient Greeks mistakenly assumed that the ability to hunt at night was the result of high intelligence, and gave us the term “wise as an owl.” But the owl brain sacrifices large sections of its brain for vision and for flying and hunting dexterity. Just don’t ask one to solve a mathematics problem.