Owls

Since ancient times, the poor owl has been associated with bad omens by many people. Our literature is filled with such descriptions as "messenger of death," "harbinger of evil," and "bird of witchcraft." Even in biblical references the owl is listed as an abomination among the fowls (Leviticus) and figures prominently in scenes of destruction and ruination. Isaiah used the owl as a symbol of misery, desolation, and decay: "And thorns shall come up in her palaces; nettles and brambles in the fortresses thereof; and it shall be an habitation of dragons, and a court for owls."

The barn owl's white, heart-shaped face, hunched back, and deep-set black eyes give it an almost ghostly look.

On the other hand, not all images are unfavorable to the bird. The owl has frequently been associated with the gods and was the special bird of Minerva, Goddess of War and Wisdom of the Romans. When writing of the defeat of the Persians, Aristophanes said:

Yet we drove their ranks before us, ere the fall of eventide,
As we closed, an owl flew o'er us, and the gods were on our side.

Sir Philip Sidney, in his "Remedy for Love," wrote: "0 you virtuous owle, / The wise Minerva's only fowle."

Owls are often portrayed as having wisdom, as in the following anonymous rhyme:

A wise old owl sat in an oak,
The more he saw the less he spoke,
The less he spoke the more he heard,
Why can't we all be like that wise old bird.

In reality the owl possesses no supernatural powers or exceptional wisdom, but it is probably the most effective mousetrap around. Owls are primarily birds of the twilight and night, although some species are diurnal, hunting during the day. Under severe press of hunger or when demanding owlets are in the nest, nocturnal species also may hunt during the day, especially when the day is cloudy or heavily overcast. Nature has well equipped the owl for its particular role in life. Its whole body is designed to make it an efficient and deadly night hunter.

Screech owls may display either a rufous (reddish or rusty brown) or a gray color phase.

First of all, the bird achieves almost noiseless flight and can swoop down on its victim unheard. Two factors work together to accomplish this. First, large wings and a light body enable the owl to support itself easily and quietly in flight. A heavy-bodied bird requires hard-working wings that tend to be noisy. If you have ever heard a startled quail take flight, you have some idea of the noise some birds' wings can make. Second, most owls' feathers are finely fringed on the edges and covered with a velvet-like pile to help deaden the sound of air movement in flight. However, some, such as the pigmy owls, have hard plumage and their unmuffled wings are not noiseless. Since pigmy owls pounce on their prey from vantage points during the early morning and late afternoon, they do not need the silent flight required by the nocturnal species.

Another advantage nature has given the owl is excellent eyesight. An owl's eye is probably the most efficient organ of vision possesed by any animal. It has a visual sensitivity at least 35 times greater than ours, and possibly as much as 100 times greater. But the owl still cannot see in absolute dark-ness. Luckily, total darkness, except in deep cave systems, is very rare in nature. On a moonless, cloudy night, which appears to be pitch black to us, the actual level of illumination rarely drops below .004 foot candles. Studies have shown that the long-eared, tawny, and barn owls can see their prey from six feet away with as little as .00000073 foot candles of illumination. It is no wonder that this fantastic night vision has given rise to so many folk tales of supernatural ability.

Small burrowing owls like to take over the burrows of other animals.

An owl's eyesight also is binocular, providing it with a single field of three-dimensional vision similar to that enjoyed by humans. Although the owl's eyeballs are not capable of rotary movement as ours are, the bird overcomes this drawback by having an extremely flexible neck, which enables it to rotate its head at least 180 degrees and possibly as much as 270 degrees. This ability accounts for the old tale that a person can walk circles around a nesting owl and cause it to twist off its head.

Exceptionally keen hearing completes the owl's nocturnal design. Some people have the mistaken idea that the tufts of feathers located on the tops of some owls' heads are ears. These "ear tufts" have nothing to do with the ears or the owl's hearing. They are merely elongated head feathers that can be erected or depressed at will, perhaps to communicate attack, withdrawal, or some other type of owl body language. They also aid the bird in its camouflage efforts. As the owl sits motionless in its alert posture, it looks like a broken upright tree stub, an illusion that is emphasized by the ear tufts.

Protruding external ears, which are so common to mammals, are not found in the bird world. That type of ear would cause air resistance when the bird was in flight. The owl's actual ears are concealed behind the edges of its facial eye disks. These large ear openings look like concave dishes. By erecting or depressing the plumage in front of or behind the ear openings, the owl is able to direct its hearing in different directions.

Owl pellets contain the indigestible remains of animals swallowed whole or in large pieces the night before.

In addition to being efficient receivers of sound, the owl's ears are especially tuned to high-frequency sounds, such as those made by squeaky-voiced rodents. Noises caused as the rodents scurry across dried vegetation, sticks, and other debris also contain a great number of high-frequency sounds that give the owl a clue to the whereabouts of its prey. Studies of barn owls have shown that this bird's excellent hearing enables it to catch living prey in absolute darkness if the rodent squeaks or rustles a leaf to give away its location.

Although rodents make up a large percentage of the owl's diet, they are not the only item on the menu. These efficient predators also eat insects, earthworms, fish, crayfish, amphibians, birds, and small animals. Food studies of owls can be quite accurate because the bird leaves an involuntary record of what it has eaten. Although an owl sometimes crushes the skull of a mouse or plucks the long wing and tail feathers from a bird, it swallows its prey whole when possible. Larger animals are torn into pieces that can be gulped down. Bones, feathers, fur, and entrails are all swallowed. The nourishing parts are digested and the indigestible parts are compressed into a pellet that is coughed up by the owl.

Owl pellets have proven quite valuable to professionals studying the relationship between predators and prey. There can be no doubt as to which prey species are being eaten by owls. Fossilized pellets also have provided us with one of the few true records of what was actually eaten by animals long dead. If you happen to come across an owl pellet, you might want to do a bit of detective work on your own to determine what that particular bird ate. The best way to find out what the pellet contains is to soften it in water and then carefully take it apart. You might even want to examine the contents under a magnifying glass or microscope.

Almost everything about the owl is unusual and interesting. Take time to learn more about it and you will probably agree that this feathered mousetrap is usually beneficial.


Additional Information:

Ilo Hiller
1989 – Owls: Introducing Birds to Young Naturalists. The Louise Lindsey Merrick Texas Environment Series, No. 9, pp. 38-42. Texas A&M University Press, College Station.

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