From Badger Run Wildlife Rehab
We mentioned in a post yesterday that owls have elongated (tube) eyes, not round or oval. So what are the advantages of an elongated eye?
If a species is going to be active largely at night (nocturnal) or dusk and dawn (crepuscular), it's going to need really large eyes to let more light in. And to capture that light and create a fixed, focused image, the eye needs to have a supersized retina in the back. A tube eye accommodates a larger retina than a round eye. It also creates a bit of a zoom-like effect making owls more far-sighted.
The other thing is that a giant tube-shaped eye is easier to fit into a relatively small skull than a giant rounded eye. Since an owl's eye can make up to 5% of its body weight, the tube shape also allows better weight distribution for flight.
You can see the prominent sclerotic rings that surround the eye on the Great Horned Owl skull in the photo by David Stang that help to support the oversized eye.
And the Great Horned owl in the photograph is our always camera-ready ambassador, Cuddly Dudley.
