Great Grey Owl Fact Sheet

Great grey owl (Strix nebulosa): the world’s largest species of owl by length.

Kingdom: | Animalia
Phylum: | Chordata
Class: | Aves
Order: | Strigiformes
Family: | Strigidae
Genus: | Strix
Species: | S. nebulosa

Size and Weight:

Great grey owls are the longest owl species, measuring 24 to 33 inches in length. Females are slightly longer than males, measuring 28 inches on average while males measure 26 inches. Their wingspan can exceed 5 feet but is 4 feet 8 inches on average. While they are the tallest owl species, they are not the heaviest. The great horned owl and the snowy owl weigh more than a great grey owl and have larger feet and talons. Great grey owls weigh 1.28 to 4.19 pounds, with females slightly heavier than males.

Appearance:

The great grey owl sports grey plumage with a white collar or “bow-tie” across its neck. The underparts are light with dark streaks and the upper parts are grey with pale bars. They have a large rounded head and yellow eyes with dark circles around them. They do not have ear tufts. These owls have the largest facial disc of any raptor, which they use like a radar dish to track sound while hunting.

Diet:

Great grey owls are carnivores, feasting on small mammals. Their prey includes voles, pocket gophers, mice, shrews, squirrels, weasels, small birds and sometimes frogs. These owls hunt both during the day and at night. They hunt listening and watching from a perch, then swooping down when it locates prey. They’re silent in flight, allowing them to surprise their target. Despite their small size, these owls are powerful and can break through hard-packed snow to grab a small mammal. One owl reportedly broke through snow hard enough to support a 176-pound human.

Habitat:

Their habitats include forests, freshwater wetlands, high mountains, tundra, and boreal habitats.

Geography:

Great grey owls are found in the northern hemisphere in North America and Eurasia. In North America, their range extends as far east as Quebec to the Pacific coast and Alaska. And in Asia, it ranges from Finland and Esonia to northern Asia. These owls do not regularly migrate but they are nomadic. Scarce winter food sometimes drives them even further south.

Breeding:

Great grey owls reach sexual maturity at 2 to 3 years old. Males and females form pairs during the breeding season in late winter. These pairs don’t stay together during the non-breeding season. They bond through mutual preening and courtship feeding. Great grey owls do not build their nests, but seek out cavities in broken tree tops or stick nests abandoned by other large forest-dwelling birds.

The female lays 3 to 5 eggs and incubates them exclusively while the male brings her food. After hatching a month later, the young are born helpless, eyes closed and completely covered in fluffy down. During their first 3 to 4 weeks, the young stay in their nest, as they cannot yet fly. Once fledged, the adult female becomes less involved and the male begins directly feeding the young. After 3 months, the fledglings are independent and find their own hunting grounds several miles from their home nest.

Social Structure:

Great grey owls are generally solitary except when mating. These owls are not as aggressive as other alpha predators when protecting their nesting or hunting territories. However, a female may be aggressive in protecting eggs and owlets.

Lifespan:

Great grey owls live between 10 and 20 years in the wild.

Threats:

Habitat loss and fragmentation through timber harvest and development are the largest threats to these owls. Other threats include fire, direct human impacts (including car strikes and hunting), predation from other birds, starvation during winter and diseases like West Nile Virus. 

Conservation Status:

As of 2021, the IUCN has classified the great grey owl as Least Concern on its Red List of Threatened Species.

Sources: National Park Service, National Audubon Society, and Cornell Lab of Ornithology.

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