Vol. 11 Issue 3, Fall 2006
By Nicole Hamilton
Barred Owl along the back roads of Loudoun, tucked into the trees
Owls ― they are rarely seen and seldom heard; yet they inhabit our forests and wetlands and keep watchful eyes as efficient, often silent, hunters of the night. World-wide, there are 134 species of owls. Here in Loudoun, we have eight species that either live here or pass through. All of the photos below were taken here in Loudoun. Our year-round residents include the Eastern Screech Owl, Barred Owl, Barn Owl and Great Horned Owl. On occasion, we see the Northern Saw-Whet Owl, the Long-eared Owl and the Short-eared Owl. The Snowy Owl is seen only passing through in a rare year, since it lives and breeds much farther north in places like the Arctic tundra, Alaska and Canada.
Owls are very unique birds that are highly specialized to be the night hunters of the avian world. Stories have been told throughout history about the mystical powers of these birds, and in many cultures they have been persecuted by humans out of fear. In truth, they are magnificent creatures, and when we see them on our winter bird walks, there are few birders who are not moved by the sight.
The adaptations that owls have gone through over the last 100 million years have refined their bodies and abilities. From the camouflage that keeps owls safe in the daytime to the refinement of their wing feathers that enables silent flight, owls are amazing.
Camouflage: Coloration is the tool that owls use for safety during the day. The colors of their feathers and shapes of their bodies enable owls to be camouflaged during the day while they rest. As they sit motionless in a branch, they are able to blend into the twigs and branches, blending into the habitat around them. Even on their eyelids, most owls have a pattern or striping, so that while they sleep they are hidden.
When threatened, owls often stay still rather than take flight. This stillness enables them to take advantage of their camouflage. To hide themselves further, owls elongate their bodies, pull in their feathers to reduce their silhouettes, raise their ear tufts (if they have them), and close their eyes. This posture is thought to be the best for blending into the surroundings. Owls can also move the feathers around their faces. By flattening or spreading their feathers, they can make their eyes appear larger or make them seem to disappear against a tree.
Feathers and Flight: Owls have two types of feathers, down feathers and contour feathers; however, with owls, the down feathers are far fewer compared to other birds. To compensate for fewer down feathers, owls have special downy barbs on the lower sections of their contour feathers. These barbs not only trap air as down feathers will, but they also enable the owl to use the feathers for double-duty, keeping the owl warm and assisting with flight.
One aspect of the owl’s primary feathers sets it apart from all other birds ― a soft frayed-looking edge along the front edge of its flight feathers. This frayed edge filters out the shock of air as it flows over the wing during flight and muffles the sound, making the owl almost completely silent as it flies. All owls, except those that primarily hunt during the day, have this adaptation.
Another interesting aspect of owl feathers and flight is the wing itself. Owl wings differ based on the habitats in which the birds hunt for food. For example, those owls that hunt over fields and marshes tend to have slender wings, while those that hunt through the woods have shorter, broader wings. All owls are powerful fliers because the size of their wings compared to their bodies is much larger than in other birds. This ratio also means that owls are built more for lift than for speed, enabling them to carry away larger prey.
Sights and Sounds: Owls have evolved to have very large eyes relative to their bodies. Having larger eyes lets in more light, allowing them to see well at night. Having pushed the limits of what their skulls could hold, the eyeballs of owls have developed as tubes rather than spheres. Because of this, owls cannot turn their eyeballs in their sockets like we can, but instead, turn their heads which can achieve terrific rotation of up to 270 degrees! While owls only see in black and white, they do see both in darkness and in bright light. Interestingly, the only mammal that comes close to being able to see as well as an owl at night is the cat.
In addition to sight, owls have terrific hearing, and their ears are unique in the animal world. The advantages that owls have for hearing begin with the shape of their faces. Having relatively flat faces, owls are able to use their face like a radar dish with their ears at the edges. This shape allows them to gather more sounds, turn their heads, and pinpoint the location and distance from which the sound is coming. To pinpoint the horizontal location of the sound, the owl turns its head left and right until both ears hear the sound equally. Owl ear openings are asymmetrical such that one ear is slightly higher than the other. When the owl tips its head, it can determine the height of the sound when it becomes equal in both ears. Once it has adjusted the sound both horizontally and vertically, it can zero in on the exact location of the prey. This acuity gives owls the ability to strike prey in almost complete darkness. Because owl hearing is so sensitive, it does not take much sound to draw the owl’s notice. A mouse scratching in a field under snow is enough to trigger the owl’s honing instinct.
Eating: Wherever small birds and rodents thrive, owls thrive, too. Occurring at the top of the food chain, owls keep the populations of these and other small creatures in balance. Owls are active year round and, as a result, need to eat every day. Barn Owls have the lowest fat reserves of just 6% of their weight, followed by Short-eared Owls with 9%. Owls are opportunistic feeders, eating what is available. While rodents, such as mice, voles, flying squirrels, rats, and chipmunks make up the majority of an owl’s diet, it will also eat things like ants, spiders, moths, frogs, snakes, and songbirds.
Owls use their feet with their strong talons to catch prey. Their feet have four toes. When resting on a branch and catching prey, they position two toes forward and two toes aft, but in flight they typically have three toes forward and one toe to the back. Their toes are strong and sharp, able to pierce through animal skins and hold tightly.
As with most birds, owls are unable to chew their food. Instead, they eat small animals either whole, often head first, or tear off pieces and swallow, allowing their digestive system to take the nutrients from the food. Because they swallow the hair and bones of animals they eat, owls need to regurgitate these, and they do so in the form of owl pellets. The pellets are formed a few hours after eating and are moved back up the throat into a special pellet-holding area just above the owl’s gizzard. The owl regurgitates the pellet before consuming more food and going on its next hunting round.
The Size Difference: With the exception of the Short-eared Owl, the female of the species is larger than the male. In the case of the Short-eared Owl, both sexes are about the same size. It is thought that female owls have evolved to be larger than males because in the world of owls, raptors often attack raptors. By being larger, females can ward off attacks by males.
Here in Loudoun, we enjoy a nice diversity of owl species, each with their own habitat needs and distinct features:
Eastern Screech Owl ― Screech owls are one of our smallest owls, with a length of about 8 1/2 inches and a wingspan of up to 20 inches. They are found in forests, swamps, and valleys, as well as urban and suburban settings. Screech owls prefer nesting in tree cavities but will also use nest boxes. Nest boxes are easy to make and will be accepted in the right conditions. Screech owls are nocturnal. Their call is a muted trill. The Eastern Screech Owl has two color phases, a red phase and a grey phase. The grey phase is found in areas where the bird needs to blend in with the bark of hardwoods, while the red phase is found in areas where the bird needs to blend in with reddish pine trees.
Barred Owl ― Barred Owls are medium sized, with a length of about 21 inches and a wingspan of up to 42 inches. Their preferred habitat is dense woods with conifers, hardwoods, and streams and wetland areas. Barred Owls are mostly nocturnal, although they may be heard during the daytime as well. Nest sites include tree cavities, abandoned crow, hawk or squirrel nests, or sometimes on the ground in low shrubs. They re-use the same nest from year to year, so if you locate a secret Barred Owl nesting spot, you may be able to see the pair there for years to come. They only lay two to three eggs per year and have up to two broods per year. The call of the Barred Owl has the familiar moniker “Who Cooks for you? Who cooks for you all?” This owl has a broad, boxy shape with no ear tufts. Its brown body has dark highlights and a pale, tan belly with dark striping.
Barn Owl ― Also medium-sized, Barn Owls have a length of about 16 inches and a wingspan of up to 42 inches. They are most often found around man-made structures such as barns, silos, warehouses, stadiums and other structures that are open. Barn Owls are nocturnal. They lay an average of five eggs and may have up to two broods in a year. Nesting sites include tree cavities, ledges in barns, abandoned buildings, and towers. In addition, they will use nest boxes securely mounted 25 feet up in a tree. Barn Owls will eat around three mice per day (1,000 per year), helping to keep the balance of rodents in check around farms, meadows and other habitats. Their call is a raspy hissing or a single shrill note. Barn Owls are reddish brown on the back, white or tan on the belly, and have a white heart-shaped face. Barn Owls are the world’s most common owl, and are found on almost every continent.
Great Horned Owl ― The Great Horned Owl is Loudoun’s largest owl, truly at the top of the food chain. Its name comes from the bird’s large ear tufts. The owl’s body is large, brown, with grayish-brown markings, and the eyes are a bright yellow. The length of a Great Horned Owl is about 22 inches and its wingspan is up to 44 inches. Primarily nocturnal, they are found in our forests, swamps and meadows. Great Horned Owls have only one brood per year, laying one to four eggs, which are incubated by the female. Nesting in abandoned hawk, eagle or crow nests, cavities in cliffs, and sometimes on the ground, Great Horned Owls often return to the same nest each year. The call of the Great Horned Owl is the familiar series of hoots.
Short-eared Owl ― Short-eared Owls are uncommon in our area but sometimes can be seen in the winter. This is a medium-sized owl, with a length of about 15 inches and a wingspan of up to 38 inches. The ear tufts are very small, almost not noticeable. The body is light brown with darker markings, and the chest and belly are white with dark markings. Short-eared Owls enjoy open fields, brush, clearing, and marsh areas. They are diurnal and can be seen hunting for mice and other creatures over fields during the early and late daylight hours. This owl nests in grasslands and forms its nest on the ground, sometimes in colonies. It lays four to nine eggs and has just one brood per year. The call of the Short-eared Owl is a series of high-pitched raspy notes.
Northern Saw-Whet Owl ― With a a length of about 8 inches and a wingspan of up to 17 inches, the Northern Saw-whet Owl is the smallest owl in eastern North America. The body, chest and belly of this bird are reddish-brown. The face is also reddish-brown but has a central white patch and no ear tufts. This owl prefers dense conifers and mixed conifer/hardwood forests. It nests in tree cavities and is nocturnal. The Saw-whet Owl is also uncommon in our area but a joy to see when we can. The Saw-whet Owl lays 4-7 eggs and has just one brood per year. The call of this owl is a series of raspy notes likened to a saw being sharpened or a whistle that is repeated.
Snowy Owl ― Every few years, during the winter, we will have reports of a Snowy Owl that has decided to come to Loudoun for a short stay of perhaps a few weeks. This owl is diurnal, hunting mostly during the day in the summer time. The Snowy Owl is even larger than our largest, year-round resident, the Great Horned Owl. With a a length of about 23 inches and a wingspan of up to 52 inches and its white body merely speckled with dark markings, this bird is quite a sight. Its habitat is the Arctic tundra, so while it may stay here for a few weeks for refueling, Loudoun is just a stopover. The call of this owl is a short series of long, deep “hoo-hoo-hoos”.
Long-eared Owl ― The Long-eared Owl is another rare sighting here in Loudoun but it has been spotted during the breeding season and one was even rehabbed here in Loudoun by one of Loudoun Wildlife’s long-time members. The Long-eared Owl is of medium size, with a length of about 15 inches and a wingspan of up to 36 inches. Their coloring is similar to that of the Great Horned Owl but they are smaller and have a more elongated body. The habitat of the Long-eared Owl includes forests of hardwoods and conifers as well as swamps. They often roost in groups in thickets and thick conifers. Like many owls, they enjoy eating mice, voles and songbirds. Their call is a single extended “hoooo” and they are nocturnal.
Backyard Owling and Attracting Owls to your Neighborhood: Backyard owling is best done first through listening. The calls of owls are quite distinct and can be found on the internet. The most common owl to listen for is the Screech Owl since they have adapted to urban and suburban areas. However, depending on the habitat of your yard and that of adjoining property, you may be able to attract other owls as well.
To attract owls, you need to provide the right habitat (food, water, cover, nesting sites) for both owls and the animals they eat. If you practice gardening for wildlife ― letting weedy edges and tangles grow, planting native plants that draw in wildlife, and leaving dead trees (“snags”) ― you may already have owls in your yard. You can learn more about gardening for wildlife through the National Wildlife Federation’s backyard habitat program and through the Loudoun Wildlife Conservancy website under habitat restoration. In addition to providing the right habitat, you can also set up nest boxes. Plans for building owl nest boxes can be found at The Owl Pages: http://www.owlpages.com/links.php?cat=Owls-Nest-Boxes .
The primary book used for writing this article:
Owls: A Wildlife Handbook, by Kim Long, Johnson Books , 1998.
Other recommended owl books:
Owls, by Connie Troops, Voyageur Press , 1990.
Owls: The Silent Fliers, by R.D. Lawrence, Firefly Books, 1997.
Now that you’ve read through the article, have some fun with our Owls of Loudoun Crossword Puzzle!
To learn more about Eastern Screech Owls and nestboxes for them, listen to our Eastern Screech Owl podcast.