Strix nebulosa | Great Grey Owl

The Great Grey Owl

An owl that hunts by ear under snow

A tall grey owl hunts the dark edges of northern boreal forest. Its face is a wide disc of fine feathers, in fact. No ear tufts break the outline. Yellow eyes sit under a dark chin mark.

The bird looks huge, yet it weighs less than a goose. Most of that bulk is loose feather. Snow muffles sound across much of its range. So the owl hunts by ear alone.

It drops onto prey hidden far below. Because the disc funnels sound to the ears, a vole under 30 cm of snow can still be heard and caught.

Family tree

Strigidae, the typical owls

The species belongs to the family Strigidae, the typical owls. Johann Reinhold Forster named it in 1772. About 20 species now sit in the genus Strix.

They share a round head and no ear tufts. The barn owl belongs to a separate family, Tytonidae. Its face is heart-shaped, not round.

Both birds hunt small mammals at night. Yet the two families split long ago, and their ear openings sit in different places on the skull.

Tall, grey and feather-light

How to tell one

Adults stand 61 to 84 cm tall. Wingspan runs 137 to 152 cm. Weight falls between 700 and 1700 g.

Females outweigh males by a little. Grey and brown bars cover the body, as well. Faint bands cross the long tail.

A ruff of fine feathers rings the face. Yellow eyes are small, while the skull is wide. Nothing on the bird is heavy, for all that loose plumage hides a body no bigger than a small hawk.

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Boreal forest and meadow edge

Where it lives

Boreal forest is the stronghold. Spruce, fir and larch all suit it. Meadow edges matter most for hunting.

Open bog gives access to voles. Northern Europe and Asia hold birds too. Its range circles the whole northern hemisphere, of course.

Tall, broken-topped trees are needed for nesting. Clear-cut blocks hold no voles and no nests. Because the owl hunts by sound, thick young plantation is almost as useless to it as bare clear-cut land.

Voles above all else

What it eats

Voles are the main prey. Mice and shrews follow close behind, in addition. Pocket gophers are taken in the west.

Squirrels, hares and weasels appear at times. Birds are caught too, grouse among them. It sits on a low perch and listens.

Then it drops, feet first. Prey is swallowed whole or torn apart. In winter the same perch is used night after night, since prey is thin and the bird cannot waste energy on long searching flights.

No nest of its own

The breeding cycle

Courtship begins in late winter. Males bring food to the female. No nest is built by either bird. Instead, an old stick nest is used.

Broken-top trees work well. Even so, cliff ledges serve in some areas. Two to 5 eggs are laid. The female sits, and the male feeds her.

Young leave the nest before they can fly. After that they stay near the nest for weeks, while both parents keep bringing food until the young can hunt alone.

Least Concern

Conservation

The IUCN rates the species as Least Concern. Its range is vast. Numbers hold up well.

Logging of old forest is the main worry, however. Nest trees take a century to appear. In addition, rodent numbers rise and fall with the year.

Thin snow years and thick snow years both cut hunting success. Unlike the osprey, which can nest on almost any tall platform, this owl needs old trees in quiet forest. That narrow nest need makes every large clear-cut a real loss, since a replacement tree will not be ready for another hundred years.

Side by side

How It Compares

Common misreadings

What People Get Wrong

• The huge size means a heavy bird. Loose feathers hide a light body.
• Owls see their prey. This one hunts mainly by ear under the snow.
• Every owl builds a nest. This species borrows one or uses a broken-topped tree.

Going further

Sources and Further Reading

• Wikipedia, Great grey owl
• IUCN Red List, Strix nebulosa. The IUCN Red List of Threatened Species.
• Animal Diversity Web, University of Michigan. Strix nebulosa.
• Mikkola, H. 2012. Owls of the World. Christopher Helm.

Quick hits

Five things to remember

• The bird is the tallest owl in North America.
• One owl can hear a vole under 30 cm of snow.
• It builds no nest of its own at all.
• Sight matters far less than hearing when it hunts.
• Loose feathers make the bird look twice its real weight.