The northern saw-whet owl (Aegolius acadicus) is the smallest of Pennsylvania’s owls, a woodland elf barely 8 inches long and weighing a little more than a robin.
Saw-whets are rusty brown below, chocolate-colored above with white spots, and with large yellow eyes. Unlike the eastern screech-owl, which is also common across Pennsylvania, the saw-whet has no feathered “ear” tufts sticking up on its head.
Saw-whets nest in tree cavities, with the males advertising their territories beginning in late winter. The most common call is a high, whistled toot, about one per second, that sounds a lot like the back-up alarm on a large truck. Other common vocalizations include catlike mews, long, eerie whines and sharp bill-snaps; click here to listen to examples of saw-whet calls.
Like all owls, saw-whets depend on sharp hearing to hunt. The loosely built feathers covering the facial disk, beside each eye, are acoustically “transparent,” and allow sounds to penetrate to the ear openings hidden below.
An owl’s ears are openings in the sides of the skull, but in saw-whets (and a few other species) the ears are significantly asymmetrical, with the ear on the left high on the skull and pointing up, while the ear on the right is low and points down. This permits the owl to pinpoint soft sounds in complete darkness.
The saw-whet owl’s strange name comes from the supposed resemblance of one of its calls to the raspy noise made by a file sharpening, or whetting, a saw. Other folk names included saw-filer, sparrow owl, whetsaw and white-fronted owl. Its scientific name, Aegolius acadicus, means “the owl of Acadia,” a reference to Nova Scotia, where the first specimen was collected in the late 1700s.
Where They Live
The saw-whet owl’s breeding range stretches from the southern Appalachians north to Nova Scotia, west across Canada and the northern U.S. to Alaska, and south through the western mountains to southern California and Mexico. Although saw-whets will use many kinds of forested habitat, they are most closely associated with conifer and mixed conifer/hardwood forests at high elevations and across the northern half of the continent, feeding mostly on woodland mice. In winter they are found across most of the United States, as far south as the Gulf of Mexico.
Because they are so shy and secretive, saw-whet are often overlooked, and have long been considered rare or uncommon in many regions, including Pennsylvania. Recent research, however, suggests this tiny owl is more abundant and widespread in the Keystone State than originally thought, breeding at least as far south as the Blue Mountain in Berks County, South Mountain in Adams County, and the Laurel Highlands of southwestern Pennsylvania.
In order to more fully understand the saw-whet’s range, volunteers with the Pennsylvania Breeding Bird Atlas have made a special effort to survey saw-whets, using recordings of their calls. Click here to see a range map based on their findings.