Denizens of the Night Add Wonder to Winter
Photo by Steven D. Bailey
Somewhere in a Chicago region woodland, a female great horned owl is sitting on her nest. The wind is blowing and snow dusts her feathers as she incubates two eggs. It’s early February, and her eggs will likely hatch even while winter still has its grip on the region.
Winter is nesting time for the great horned owl, one of nine species of owls that can be found in the region year-round or part time. The great horned, along with the barred owl and eastern screech-owl, are year-round residents. In some years, the rare (state-endangered) barn owl also may be found in the Chicago region in all seasons. In autumn, the northern saw-whet owl, short-eared owl, long-eared owl and snowy owl migrate through and/or spend winter here. The burrowing owl, considered a vagrant, has also occasionally been seen in the Chicago area.
These elusive raptors have many adaptations that enable them to catch prey at night and avoid detection by predators and humans. For example, many species of owls have a velvet-like substance called a nap covering their feathers, which muffles the sound of the feathers rubbing together when flying.
Specialized hearing and eyesight
Owls also have keen eyesight. Compared with humans, they have more rod-shaped cells in their eyes, which are highly sensitive to light and movement, enabling them to see a mouse running across the landscape. Owls also can see very well during the day, and it’s not unusual for some species, such as a barred owl, to capture prey when it’s light.
Owls can’t move their eyes from side-to-side, but they can rotate their heads up to about 270 degrees to see what’s happening around them. An owl’s facial disk, a group of feathers around the eyes, works like a satellite dish, trapping the sound and bringing it to the ears, which are small holes on both sides of the head, one higher than the other. This asymmetrical arrangement helps an owl triangulate on its prey. The great horned owl’s “horns” are not ears, but tufts of feathers used for communication and display.
Most owl species regurgitate undigestible parts of their meals, which include fur and bones, within pellets. Seeing pellets below a tree indicates an owl visited the area and might even still be close by.
The most abundant and mysterious-sounding owl in the Chicago area is the eastern screech-owl. It gives haunting calls at night that sound like a horse whinnying, followed by a series of tremolos. Strictly nocturnal, this owl, which can be reddish or grayish, is robin-sized, with a 20-inch wing span. It has tiny ear tufts and yellow eyes. The screech-owl nests in suburban yards and city parks, as well as forest preserves. Its typical habitat is young woods near water. The female lays up to six eggs in a tree cavity, often carved out by a woodpecker. Erecting a screech-owl nesting box could entice it to nest or roost.
The great horned owl, also quite common, stands up to nearly 25 inches tall, with up to a 57-inch wingspan. It’s most vocal in fall and winter, when mating begins. At dawn or dusk and into the night, a pair repeats a series of five to eight hoots. The female lays eggs in an abandoned squirrel, crow or raptor nest. Seven weeks after hatching, the young make short flights, but they continue to beg for food all summer from their parents, giving unusual shriek calls at night.
The barred owl, less common in the Chicago region than in other parts of the state, can be quite vocal, even during the day, in suburban parks such as those in the Palos area. It gives a riotous call described as, “Who cooks for you? Who cooks for you all?” Males and females also give monkey-sounding calls when pair bonding. It nests in large tree holes in mature woodlands, often near water. The barred owl is nearly the size of a great horned owl, but it lacks ear tufts and has dark, instead of yellow, eyes and a yellow bill, instead of a dark bill. Both the eastern screech- and barred owl begin nesting later than the great horned.
A boreal forest resident, the uncommon northern saw-whet owl is even smaller than a screech-owl, and visits northern Illinois in winter seeking food, mostly white-footed and deer mice, and shelter. Compared with the screech-owl, the saw-whet has no ear tufts and has thin, white streaking on its forehead. In winter, it often roosts low in red cedars, hemlocks and other small conifers, as well as in vine tangles during the day, sometimes returning to the same spot for days or weeks at a time, or even the entire winter. Sometimes birders discover a saw-whet owl and can lead others to see it; this bird is rather tame and won’t fly away, but instead sits still to camouflage itself against tree bark.
About the size of a crow, but much bulkier, is the short-eared owl, which hunts in grasslands throughout the region as long as snow doesn’t get too deep. At dusk and dawn, it flies low over the grasslands like a large moth hunting for its prey of voles. Endangered in Illinois, the short-eared owl sometimes breeds in large grasslands throughout the state, but rarely in the Chicago region. Places to search for short-eared owls during winter include Bartel and Orland Grasslands, both near Tinley Park, Rollins Savanna, in Grayslake, Pratt’s Wayne Woods, in Bartlett, and Glacial Park, in Ringwood.
Uncommon to the Chicago region, but an occasional visitor, the long-eared owl spends most of its time during the day in conifers. Up to 16 inches tall with a wingspan close to 48 inches, the long-eared owl is very wary of intruders. It often roosts in groups; one year, a roost of up to 200 birds spent part of the winter at the Morton Arboretum. Another year, several long-eared owls wintered in a downtown Chicago park, a most unusual occurrence.
Among the most iconic owl of the Chicago region in winter is the 20-to-27-inch tall snowy owl, which breeds across the Alaskan and Canadian Arctic on the treeless tundra. In winter, some snowy owls fly south, roosting and hunting along lakeshores, in airport and agricultural fields and other flat areas. They also perch on utility posts and street lamps, barns and even city buildings. One year, just a few may be spotted in the Chicago region; other years they come in fairly large numbers, which is called an invasion. Snowy owl invasions have been occurring for centuries, and is likely related to food availability and number of young raised on the breeding grounds.
Knowing an owl’s preferred habitat and searching for pellets and whitewash, or excrement, beneath vegetation can help someone to discover an owl. The key is patience and being careful not to disturb them, especially when a great horned is on its nest or when other owls are resting on their day roost. It’s best to join a local birding group or attend a nature center program on spotting owls.
Sheryl DeVore is the author of four books on birds, including Birds of Illinois and Northern Flights. She also writes nature and science articles for national and regional publications. Contact her at Sheryl.DeVore@comcast.net.
A Free Owl Program will be held at 4 p.m., February 9, at Plum Creek Forest Preserve, in Chicago Heights. Call 708-946-2216 to register.