Where owls see so much better than we do is in the dark.
Sort of myth: Owls are nocturnal.
Some species are out primarily at night (like Barn Owls), but some are out more at dawn and dusk (like Great Horned Owls), and some are out during the day (like Burrowing Owls).
Though owls aren’t ONLY nocturnal, most hunt in the dark and if we look at the eyes of an owl, we’ll see big adaptations for seeing well at night:
- Their eyes are huge compared to the size of their bodies
- Their eyes are designed to pull in as much light as possible
- And their eyes are designed to register every bit of light that gets in
Let’s start with what a human eye looks like. If you look in a mirror, you’ll see in the very middle a black pupil, then the colored iris around it, and then the white of your eye around that. Our pupils get bigger to let in more light and smaller to let in less.
If you look at an owl’s eyes from the front, you’ll see that black pupil in the middle and around that you see the colored iris, but you don’t see any white. By being so big, the owl’s cornea lets a lot more light in than ours does. And the pupil can also be much bigger than ours again letting more light in.
Here’s what a human eye looks like from the side:
Here’s what an owl’s eye looks like from the side. It’s not round! It’s shaped a little more like a telescope! By being so big, the owl’s cornea lets a lot more light in than ours does. And the pupil can also be much bigger than ours again letting more light in.
But there’s more! At the back of our eyes, we have rods and cones to register the light. A rod needs just a single photon to be activated, but they can’t tell color, just dark or light. Cones can see color, but need more light to be activated. Because we have lots of cones, we can see color really well during the day, but we don’t see so well in the dark. Owls also have rods and cones (though a little different from ours). But they mainly have rods. That means they don’t see much color, but they see really well at night.
And, just in case a little bit of light makes it past all those rods, it’s thought that owls have what’s called a “tapestry of light” or “light shine” behind the receptors. Errant photons are bounced back into the eye to get another chance to be seen.
Owls aren’t the only animals with this “tapestry of light”. Among animals with a tapestry of light are cats, some dogs and even some fish!
A great place to read about owls is owlpages.com.
Note: This post came from presentations done by me and Mary Blake.