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 great deal like the back-up alarm on a large truck. The owls make a number of other calls, including one that sounds like someone sharpening, or "whetting," a saw -- hence the species' name.

Shy and secretive, the saw-whet owl's breeding range stretches from northern Pennsylvania to central Canada west to southern Alaska and south in the Rockies to Mexico; a small population also lives in the southern Appalachians. It was long considered uncommon, but recent research suggests this tiny owl is more abundant and widespread than originally thought, breeding in Pennsylvania 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 the breeding season, they are often found in or near conifer forests, and their major food seems to be small mammals, especially woodland mice. In winter they are found across most of the United States, as far south as the Gulf of Mexico.

Thanks to bird banders, scientists have known since the late 1970s and early '80s that saw-whets migrated through the Great Lakes states and along the mid-Atlantic coast. No one realized that large numbers of the owls also migrated through the central Appalachians of Pennsylvania until 1996, however, when biologists Eric and Melonie Atkinson and Todd Bauman began netting saw-whets near Kempton, Berks County. The following year, with support from the Wild Resource Conservation Fund, a statewide network of saw-whet banding stations was launched, including a site at the Ned Smith Center for Nature and Art. Today, there are more than a dozen owl-banding stations across Pennsylvania, including three operated by the Ned Smith Center in Dauphin, Cumberland and Schuylkill counties.

The owl migration begins in early October, peaks around Halloween, and usually ends by Thanksgiving. The largest numbers are caught on nights with a moonless sky, calm or light winds, and chilly temperatures. A northbound spring migration passes through central Pennsylvania in late February and March. But there is still much to learn about saw-whet owl migration and ecology. No one knows if they follow mountain ridges, as do hawks, or if they simply fly north and south across the landscape like migrating songbirds and waterfowl. We do not understand their habitat needs, or how far individual owls travel. (One owl, banded in Berks County, flew 175 miles to Assateague Island, Maryland, in just two nights.) Knowing more about saw-whet owl migration is crucial for managing and protecting this unique creature for future generations.