Owls

Due to their nocturnal nature, owls have been viewed as bad omens or messengers of misfortune and even death. In spite of this, owls are particularly valuable as rodent predators. A single barn owl can eat over a thousand mice in a year!

Owls play a significant role in controlling mice populations. 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 which muffle sound as the owl approaches its prey. The eastern screech owl likes to hunt from lower perches about 6 to 8 feet off the ground, and is the most omnivorous, eating insects, amphibians and warm-blooded small animals. The barred owl hunts from higher heights, relying in the winter on hearing the sounds of animals moving in the leaves or snow. The great horned owl hunts from high perches or by gliding and diving to its prey, which can be larger rabbits, birds and other small animals.

Owls probably have the most acute hearing of any bird. 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. The owl's entire face acts as an outer ear. The face is shaped like two satellite dishes that funnel sound to the ears. The compact facial feathers aid in the funneling process. The “ear tufts” on screech and great horned owls are not associated with the ears, but are thought to be a defense mechanism to help make an owl’s appearance more fearsome, like a mammalian predator, or to help them blend in to their surroundings.

In general, all birds have relatively large eyes compared to the size of their head. But 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 moving its eyes, to follow an object.

Barn Owl

Credit: wikimedia.org - Thomas Barnes, USFWS

Contrary to popular belief owls have excellent vision both in daylight and at night. 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, they 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 types of animals an owl is eating.

Owls do not build their own nests. Instead they use old hawk nests, squirrel nests, natural cavities, buildings or constructed boxes.

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.

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 to knowledge and wisdom. Their importance to our environment has also changed. As more and more land is developed, more 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.

Barred Owl

Credit: pinterest.de - Garth McElroy

Being out in the woods as dusk begins to settle, one can sometimes be startled by a loud call that sounds like “who cooks for you, who cooks for you, oo aw.” This is the call of the Barred Owl, often called a hoot owl. Often this call will be answered by other birds in the distance.

Barred owls are large, stocky owls with black or gray barrings on their chest and face. These owls do not have ear tufts like the Great Horned owl. Barred owls normally live in large tree cavities, and prefer more mature deciduous forests where these trees normally exist. Barred owls seem to prefer forests around bottomlands, near rivers, lakes, or other water bodies, but they are found in upland areas, as well. Barred owls seem to be moving into more urban areas where there are more mice and other rodents, but they are limited by the need to live in large trees, and they are very prone to being struck by cars as they dive down toward prey on roadways.

Barred owls are general predators, targeting mostly mice, rats, squirrels, and other rodents. However, they also prey on small birds, snakes, frogs, crayfish, and other reptiles. Barred owls are most active at dusk or dawn; their large eyes enable very good vision in diminished light conditions. Unlike many birds, barred owl populations are stable and increasing slightly and they seem to be well adapted to living around humans.

The barred owl is found throughout the east, from Florida to Canada, and in fairly recent times, has expanded its range across Canada and the Pacific Northwest. The barred owl occupies the same niche in the Pacific Northwest as the rare Northern Spotted owl. The more aggressive barred owl is viewed as a threat to the spotted owl where their home ranges overlap.

Eastern Screech Owl

The Eastern Screech Owl, Megascops asio, is a year round native of Maryland. This bird is a night hunter that eats mice, insects, worms, and small birds, including songbirds and starlings. They regurgitate pellets containing bones, feathers, and fur of their prey. Investigation of the pellets located around their nesting areas can provide information about their diet.

Their large eyes are well adapted for night vision. The adults are short, stocky birds, typically around eight inches tall. They have tufted “ears,” which are only feathers, that aid in their concealment. The length of the tufts vary widely in different birds. Coloration of the birds is typically grey or rusty brown.

Screech owls are usually monogamous, and mate for life. Males are smaller than the females. These birds are well adapted to suburban areas where they fledge more chicks, possibly due to less predator competition for food. Like other predator birds, they fight fiercely for food with weaker siblings, sometimes being driven from the nest. They are not endangered, and their numbers are increasing. Screech owls roost in dead trees or snags where available. They will sometimes nest in backyard boxes if provided for them.

Screech owls have a strange sounding call, which is not actually a screech, but is more likely to sound like a unique single low tone warble in males, and a higher sound that has been likened to the whinny of a horse in females. These sounds may not be completely related to the gender of the birds. In addition to their night calls, they can sometimes be located in the day by the commotion of birds flying around their resting areas, which warn others of the danger from the small predator.

Great Horned Owl

These large birds are year-round residents of Frederick County. Their feathered tufts give them a distinctive look. This bird is often depicted in cartoons with horizontal ear tufts and eye glasses as the “wise old owl”.

Great horned owls (Bubo virginianus) are widely distributed, and are easily recognized by their hooting call which has also caused them to be called “hoot owls”. They are widely distributed in Frederick County, and they can often be heard locally. If you live in a suburban, reasonably quiet location, you can, many evenings or early mornings, hear them calling back and forth.

Great Horned Owls are up to two feet tall and have up to five foot wingspans. Their coloration is a mottled grey brown, a reddish tint on their face. Typical of all owls, they have huge eyes and excellent night vision. The feathers, also like other owls, are adapted for silent flight. They can use differential hearing to locate prey in the darkest nights.

Great Horned Owls are adaptable to a wide variety of habitat, including evergreen and deciduous forests.

Generally nocturnal hunters, upon occasion, they will be seen seeking prey in the daytime. Occasionally during the daytime, a mob of crows will be seen attacking owls, which are their mortal enemies. Great Horned Owls prey on mammals such as rabbits and groundhogs, among others. They also prey on birds such as crows and ducks. They are also capable of killing large birds of prey such as hawks, ospreys and other owls.

Much has been written and available about the Great Horned Owl, and a number of on-line sources of recordings of their calls are available.

Northern Saw-Whet Owl

Credit: BowersPhoto.com - Rick & Nora Bowers

The Northern Saw-Whet Owl, Aegolius acadicus, is Maryland’s smallest owl, and is rarely seen in Frederick County. They are an endangered, threatened migratory bird. They are preyed upon by other owls and raptors. Sometimes they winter over in Maryland and are found most often in the western part of the state. These North American native owls are one of the smallest— smaller than the Screech Owl, and are about the size of an American robin.

Saw-Whets are so named because of their call, suggesting the sound of a saw blade being sharpened. Others have described the call as sounding like a pan flute playing a single pulsed note repeatedly for long periods.

This small owl has no ear tufts, has mottled brown to reddish color. It has a whitish face with a white spots on the head, black beak, and yellow eyes. It is quite a shy and attractive little bird. It has excellent hearing, and uses the difference in time of arrival and amplitude of sounds to locate its prey on even the darkest of nights.

Saw-Whet Owls are nocturnal forest birds which roost mostly at eye height in dense cover, most often in thick cover of evergreens next to the trunk. They feed mostly on small mammals such as mice and voles.

Nesting is mostly in abandoned woodpecker holes or other tree cavities. The female lays a clutch of 4-6 eggs, and when the young birds hatch, she feeds them while the male hunts. The female will sometimes leave the young to the complete care of the male, breed with a second male, and raise a second hatch in a single season.

Extensive efforts have been made by various groups, including some from the Frederick area, to net and band the Saw-Whet during the migratory seasons in a effort to better understand the migratory patterns and to access their numbers.

Article by Claude Eans, FCFCDB Member

Nature note for 7/14/2019