The first ever Cook County Owl Census will be taking place this weekend. We already have a breeding-bird survey that takes place in June, but that survey tends to miss owls both because the surveyors usually work in the daytime and because owls nest very early in the year; by June the peak of the season is past, and the animals are much less conspicuous.
Great horned owls tend to prefer woodlands, but they have the sort of flexibility you might expect from a bird whose breeding range extends from the Arctic Ocean to the Strait of Magellan. The claim has been made, and nobody has refuted it yet, that the great horned owl is the only bird that nests in every county in the continental U.S., including Alaska.
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Pound for pound, great horned owls are the champion predators of North America. Their diet includes rats, mice, rabbits, skunks, house cats, rattlesnakes, birds up to goose size, and, of course, screech owls. Screech owls tend to be very circumspect when they know there is a great horned owl in the neighborhood.
After dark the best way to find an owl is to imitate its call. You can do this with a tape recorder, using prerecorded calls, or you can learn to make the noise yourself. Using a tape always seems like cheating to me. It’s like lip-synching to a record or being an Elvis imitator.
Sometimes you can find screech owls by banging on the trunks of hollow trees. Screech owls nest in holes in trees, and if you knock on the trunk, a bird may stick its head out of its nesting hole to see who’s there.
The Illinois Department of Conservation is putting out owl houses here and there, but the effort has a certain forlorn quality about it. It’s like somebody putting a light in the window for a sailor who vanished in a storm five years ago and has never been seen since. There are so few barn owls left in Illinois that there is almost no chance of one finding a house.
Short-eared owls are open-country birds that often come out to hunt during the day. They hunt by flying low over the ground with a light, buoyant, almost mothlike wing beat. They will hunt over uplands, but they prefer low ground, sedge meadows, wet prairies, and marshes. I am told that about 30 pairs of short-eared owls breed every year in northeastern Illinois, but none of them nest in Cook County.
