Winter 2005

Great Horned Owl
Winter Hooter

Just before midnight on Halloween, an owl began hooting beneath a full moon in my Mundelein, Illinois, neighborhood. Wrapping a robe around me, I went outside. Across the street, a great horned owl, Bubo virginianus, sat motionlessly in a walnut tree that had just lost its leaves. The owl raised its head up and down, broadcasting its mating hoots. Three more owls joined in, vocally jousting for nesting territory. Suddenly, the first owl rose from its perch, spread its wings, and disappeared silently.

	Photo by Richard Fisher.

I have never forgotten that eerie experience right outside my front door. Many residents in Chicago Wilderness neighborhoods can experience the great horned owl near their yards as well, provided the owls have enough habitat for hunting nearby (they need about 40 acres of grassland or fields adjacent to woods in the breeding season). The species is common throughout North America and parts of South America.

The great horned owl is surprisingly large — perched, it's about as tall as a standing Canada goose. Its "horns" are not ears, but tufts of feathers that help to camouflage the bird during the day. Some biologists believe the owl may be able to signal danger to its brethren by lowering these tufts. Nature gave owls loose, soft feathers for silent flight, which explains why I didn't hear a sound as the large owl poised above me left its perch.

Like other owls, the great horned comes well equipped to hunt at night, although it can also see well during the day. Its vision is probably 100 times more powerful than a human's. The owl cannot move its large eyes much because they are surrounded by bone for protection, but a flexible neck helps the owl rotate its head 270 degrees to see its surroundings. The ears, hidden slots at the sides of the head, are positioned asymmetrically — one higher than the other — which helps it hone in on the sound of prey. Its hearing is as keen as its sense of smell is poor: a great horned owl is one of the few predators that readily eats skunks.

The owl's long sharp talons help it seize prey, which could be just about any small or medium-sized mammal or bird, including shrews, rabbits, skunks, blackbirds, and other owls. An owl cannot digest the bones and feathers of prey; instead it coughs them up in a pellet. (Some science supply houses sell these pellets to schools for children to dissect. To dissect your own virtual owl pellet, visit KidWings.)

Unlike most breeding birds of the Chicago Wilderness region, the great horned owl starts a family in the depths of winter. This timing allows the young to hatch and mature just in time for the emergence of easy prey — baby rabbits and other young mammals.

During courtship, typically several weeks in early winter, the male and female hoot off-key duets at dusk and into the night. The owls also bow to each other, droop wings, and touch bills.

Instead of building its own nest, the great horned owl seeks out a used stick nest left behind by a hawk or crow. By January or February, the female is sitting on two or three eggs, motionless as the winter winds and snows blow her feathers. She usually remains on the nest, keeping the eggs warm, waiting for her mate to bring her food, though each pair has its own arrangement of how to keep the eggs warm and themselves fed.

After the young hatch, the adults must spend several months or more bringing food to the young at the nest and teaching them to fly and catch prey. It will be another two years before the young are old enough to begin nesting. Listen for their hoots around dusk, as the first snows dust the woods.

— Sheryl De Vore