I woke abruptly, not knowing what exactly had punctuated my sleep. It was still dark and I listened intently. This time I heard it…hoo-hoo-hoo-haaw. A barred owl called from the woods. Soon another owl, slightly farther away, responded. I drifted to sleep as the pair continued to call, one enticing the other a little closer.
Because of their nocturnal nature, owls have been viewed as bad omens or messengers of misfortune and even death. In spite of their sometimes sinister appearance and ghostly calls, owls are particularly valuable as rodent predators. They are actually quite beneficial, economically: A single barn owl can eat more than a thousand mice in a year!
Formidable hunters, owls arrive upon their prey without a sound. A modification to their flight feathers makes this possible. The wings have downy fringes along the stiff flight feathers that muffle sound as the owl approaches its prey.
Owls probably have the most acute hearing of any bird. They can hear sounds 10 times fainter than a person can detect. Several features of an owl’s ear make this possible.
Owls have an extra-large ear opening surrounded by deep, soft feathers that funnel sound. Furthermore, the feathers over the ear, the auriculars, are modified to be loose and airy.
Owls also have a moveable flap of skin controlled by muscles around the ear opening. This flap protects the ear and concentrates sound waves coming from behind. Many owls also have asymmetrical ear openings. The opening in one ear will be higher than in the other ear. A sound coming from above will sound slightly louder in the ear with the higher ear opening. This allows the owl to pinpoint its prey accurately.
Finally, the owl’s entire face acts as an outer ear. The face is shaped like two satellite dishes that funnels sound to the ears. The compact facial feathers aid in the funneling process. Some owls have ear tufts, feathers sticking up on the top of both sides of the head. Ear tufts do nothing to improve hearing. Ear tufts make the owl appear larger, which helps to ward off predators.
In general, all birds have relatively large eyes compared to the size of their head. A human eye weighs less than 1 percent of the weight of the head. But owls have the largest eyes. In fact, if people had eyes proportional to those of the great horned owl, our eyes would be the size of grapefruits and weigh 5 pounds!
Owl eyes are so large that there is little room in their skulls for eye muscles. Thus, an owl turns its head, sometimes as much as 270 degrees, rather than move its eyes to follow an object.
It’s been said that the difference between the hunter and the hunted is evident in the eyes. The hunted have eyes on the sides of their heads to obtain a wide field of view. Hunters have eyes on the front of their heads to increase depth perception. Owls have the most frontally positioned eyes of any animal.
Contrary to popular belief, owls have excellent vision both in daylight and at night. Their pupils are huge at night, letting in great quantities of light and in daytime shrink down to the size of a pinpoint. Their eyes are 10 times as light-sensitive as human eyes. This is due the concentration of light-sensitive rods in the retina but is at the expense of color defining cones. So, although they see well in dim light, owls see little color.
Because they swallow their prey whole or nearly so, owls regurgitate pellets containing undigested parts of their prey. They can digest all but the bones, feathers or fur. They eject this matter in the form of a hard fur or feathered pellet.
By dissecting pellets, scientists are able to determine just what animals an owl is eating. Even if they eat insects, the pellet will contain the hard exoskeleton.
Owls do not build their own nests. Instead, they use old hawk nests, squirrel nests, natural cavities, buildings or constructed boxes.
There are several species of owls that inhabit the Chesapeake Bay region. Probably the most familiar of these is the great horned owl. This large brown owl is noted by its large yellow eyes, white throat patch and large ear tufts. It can be recognized by its call—a series of low hoots: hoo-hoo hooo hoo-hoo. Another “eared” owl is the long-eared owl, which is similar in appearance to the great horned except that its ears tufts are closer together and it is smaller and slimmer.
The eastern screech owl is a small—8 inches long—eared owl with coloring varying from rust to gray. Its call is a long quivering whistle.
Of the earless owls, the barn owl is easily recognized by its light colors and heart shaped face. As the name implies, the barn owl nests in barns, abandoned buildings and tree cavities. Its song is a long, raspy screech.
The barred owl is often referred to as the “hoot owl.” Its call is made of nine hoots that sound like the phrase Who-cooks- for-you, who-cooks-for-you-all?
The northern saw-whet owl is the smallest of the eastern owls—7 inches long—and is often found roosting in dense evergreens or in thickets. Its call is a series of toots or whistles.
Owls have been the subject of much misunderstanding, superstition and fancy. Over the centuries, people’s views of these wonderful birds have changed. They have been used to represent doom and evil as well as knowledge and wisdom. Their importance to our environment has also changed.
As more and more land is developed, many of our natural predators are lost. Left unchecked, rodents and other small mammals can become pests. Owls continue to play a significant role in our ecosystem by controlling these populations.
Putting ecological benefits aside, though, I just love falling asleep to the eerie hooting of an owl on a cold winter night.