A Hoot in’ Good Time—All About Owls

A Hoot in’ Good Time—All About Owls

By Alan Knothe, The Birdman

I have always been interested in owls, but I think they became my favorite birds when I worked at Frost Valley YMCA in New York State. There at the outdoor education center, among my other duties, I helped in the care of four non-releasable birds: Lady, an American Crow; Isabo, a Red-tailed Hawk; and Bilbo and Hamlet, both Great Horned Owls. In taking care of the birds and in using them as teaching tools with the guests who visited Frost Valley, I learned a lot. I hope to share some of my owl knowledge with you in this article.

As you may already know, there are two families of owls, the Typical Owls (Strigidae) and the Barn Owls (Tytonidae). The Strigidae contains about 140 species world wide, 17 in North America. The Tytonidae contains only 11 species worldwide and 1 in North America.

What makes the Barn Owls different from the Typical Owls? Well, the most obvious field mark is the shape of their facial disc. It is heart-shaped rather than round like in the Typical Owls. Barn Owls also have long legs and short, usually squared tails. Another difference is found in the talons. The inner edge of the middle claw is pectinated, meaning it is serrated and is used to clean the bird’s feathers.

I think what fascinates me most about owls (other than their magnificent beauty) is the incredible adaptations they posses. As you know, most owls are crepuscular (most active at twilight) or nocturnal (most active at night). They are extremely well adapted to hunting in low light conditions.
The first of these nocturnal adaptations is excellent eye-sight. Owls, as with most birds, have eyesight that is about seven times better than a person’s. This does not mean that things appear seven times closer, like looking through a pair of binoculars. Instead, things appear seven times more clearly to a bird than to man; they can distinguish seven times more detail than we can. But if other birds can see as well as owls, why can owls hunt at night and most other birds have to restrict there hunting to daytime hours? The answer lies in eye size. Owls have massively large eyeballs. In fact a Great Horned Owl’s eyes are so large compared to its skull that if a person’s eyes were equally large com-pared to his skull, the person’s eyes would be the size of grapefruits. Possessing a very large eyeball allows the owl to open its pupil very wide in low light conditions thus al-lowing more light to strike the retina.

Another way owls see better at night than most other birds is they possess a greater concentration of rods on their retinas. There are two kinds of light sensitive cells on the retinas of birds and other animals, the rods and the cones. Rods see best at night and cones see best during the day. Owls have a high concentration of rods thus giving them great night vision. Do not be mistaken, though, even owls can see better during the day than they can at night. They hunt at night simply because there is more prey active at night and because the prey is easier to ambush in the dark.

Another nighttime adaptation owls possess is an excellent sense of hearing. A person has one ear on each side of his head. This allows him to tell which direction a sound is coming from (i.e., the sound is louder in the ear that is facing the noise). Owls also have ears on both sides of their heads, but do not look for them. You will not see them because an owl’s ears are simply holes in the sides of its head. (Bulky, protruding ears would be a hindrance when flying.) These holes are very special however. One hole is slightly smaller than the other, and one is slightly higher on the side of the owl’s head than the other. This allows the owl to not only tell the direction a sound is coming from, but it can also tell exactly how far away the animal is that is making the noise, and the owl can tell if the animal is on the ground, in a bush, up a tree or even under the snow. Yes, owls can hunt mice, voles and other animals under the snow in the winter (unless the owl lives in Florida) by listening for them. Owls can hear so well that in a 1962 study by Payne it was found that Barn Owls could easily locate their prey in absolute darkness using only their sense of hearing.

Another nighttime adaptation is the owl’s ability to fly almost without making a sound. This allows the owl to ambush prey without being heard, and it also keeps the noise of flight from interfering with the owl’s ability to hear its prey. How does the owl fly so quietly? He has special feathers. The front edges of the owl’s primary flight feathers are lined with soft, down-like barbs. These barbs reduce the vortex noise of the air passing over the owl’s wings and allow it to fly silently.

I hope you have enjoyed this article. If you have any questions about owls or other things, feel free to send me an e-mail message at birdman8@cox.net. Good luck and good birding.