Awesome Facts About Owls

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Migration

flammulated: having a reddish color
Most owls do not make long migrations. They usually live in the same place all year long. One exception is the insect-eating flammulated owl. These owls migrate south each fall to find the insects they need to survive.

Sometimes, owls are forced to move because their prey becomes scarce. When this happens over a large area, many owls may leave their home territory and travel far to find food. This is called an "irruption" and it can be very spectacular as thousands of owls move into an area to find food.

Such an irruption of owls happened several winters ago in Minnesota. Birdwatchers all over the state were thrilled with sightings of several owl species rare to Minnesota. Residents of western mountain towns are sometimes treated to mini-irruptions of their own as owls living at higher elevations move down in elevation to find food during harsh winters.

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Eye See You!

Owl eyes are one of this raptor's most amazing adaptations. Their eyes allow them to navigate through their habitat in the dark. Owls that hunt during the daytime use their eyesight to find food. And owl eyes are one of the things we notice most about these birds.

Owl eyes are very large. They are so large that they cannot move in their sockets. You can roll your eyes, but not an owl. Owls also have a smaller visual field than you do.

To see what your visual field looks like try this experiment. Hold your arms out with both of your index fingers in front of your nose. While you stare straight ahead, move your arms in an arc toward your sides. When you can no longer see your fingers stop moving your arms. The arc that your arms made is your visual field and measures approximately 180 degrees. An owl's visual field is about 110 degrees. For an owl to focus well, it must turn its head to get an object into its visual field. In addition, owls often bob their heads up and down to judge distance.

rod cells: rod cells are responsible for helping to see in low-light situations
Seeing well in the dark is the major function of an owl's eyes. The size of an owl's eyes is very important for seeing at night. Because the eyes are so large, they have a large surface area to collect light. The light hits specialized cells in the eye that help animals see in low light levels. These cells are called rod cells. Owls have many more rod cells than other animals.

tapetum lucidum: this is also called "eyeshine" - the bright reflection due to a reflecting layer immediately behind the retina of the eye of many animals
In addition, owls have a structure called the "tapetum lucidum" at the back of each eye. Light goes into the owl's eyes and hits the rod cells. It then bounces off the tapetum lucidum to hit the rod cells again. This lets the owl see the light two times instead of just once. And for an owl, this turns the night into day.

You can see the tapetum lucidum when you shine a light at an animal at night. That glowing yellow or green eyeshine you see is actually the tapeta bouncing the light back into the eye. These structures, along with a large surface area and high numbers of rods, work together to give owls exceptional night vision. As a matter of fact, an owl can see three times better in the dark than you can. Check out this demo of how the nictitating membrane works (second eyelid.)

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The Better to Hear You

Because owls have such big eyes and good vision, we tend to think that they hunt by sight. Amazingly, owls hunt mainly by sound. Could you find your dinner by listening for it?

The first thing you need to know about owl ears is that they are not on the top of the owl's head. Those "ears" you seen on a number of species are feathers called "ear-tufts" and they have nothing to do with hearing. There are several things that work together to give owls excellent hearing.

The first are the facial discs. These discs surround the owl's face and give the bird its distinctive look. Made of several kinds of specialized feathers, the facial discs collect sound around the owl's head, just like a satellite dish collects signals for your television.

Another neat adaptation owls have is asymmetrical ear placement. This means that owl ears are not directly across from one another on the bird's head.

If you put your fingers in your ears and look in a mirror, your fingers will both be at the same height. If an owl put its talons in its ears, one talon would be higher on its head than the other talon. Having asymmetrical ear placement means that sounds reach the owl's ears at different times.

As the owl lowers or raises its head, it can position its head so the sound reaches both ears at the same time. When this happens, it means that the source of the sound is directly in-line with the owl's face. Some species of owl also have a moveable ear flap that they can use to increase or decrease the sound coming to their ears.

So, how well can owls hear? Have you ever heard the saying "you can hear a pin drop?" Well, an owl probably can! A great gray owl sitting on a fencepost 60 feet away can locate a vole running in a tunnel under 18 inches of snow. A barn owl can capture prey when blindfolded. However, they cannot capture prey if one of their ears is plugged or if they lose their facial disc feathers. For owls, when it comes to finding food, listening is definitely better than looking.

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What's For Dinner?

prey: an animal that is hunted or seized for food by a predator
Owls are predators. They eat many different kinds of prey depending upon their own size. Small owls such as Pygmy owls and saw-whet owls are small so they usually hunt for large insects and small rodents like shrews and mice.

Owls pretty much eat whatever they can get their talons on. But the most common prey animals are the small rodents such as mice and voles. These little mammals are important food sources for many animals. They can also be serious pests for people.

Larger owls also capture bigger prey like voles, woodrats, rabbits and squirrels. Great horned owls will even catch and eat skunks-----yuck! Other prey includes scorpions, lizards, snakes, frogs, toads, birds, bats and even fish.

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How Much Do they Eat?

Farmers can lose huge amounts of crops and stored grains to rodents. Lost crops means lost money for the farmer. Owls play an important role in keeping these potential pests under control. And they do it all for free!

If you do the math, you will find that one barn owl needs to eat about 79 pounds of mice a year. During its 10 year lifespan, that turns out to be around 798 pounds of mice. Which is about 12,775 individual mice!

Each of these mice needs to eat approximately 10% of its body weight each day. And 12,775 mice will eat almost 31,000 pounds (15 tons) of food each year. Wouldn't you like to have a few barn owls living on your farm?

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