Great Gray Owl Life History

Habitat

Habitat ForestsIn Canada, Great Grays spend the year in dense, wet evergreen forests of the far north, also known as taiga, where they hunt in meadows, bogs, or other open areas with a few scattered trees. In the United States, they use pine and fir forests adjacent to montane meadows between 2,500 and 7,500 feet. In California and Oregon during the winter months, owls often move downslope into oak woodlands and lower elevation mixed deciduous and evergreen forests. Back to top

Food

Food MammalsSmall mammals such as voles, pocket gophers, mice, moles, chipmunks, and lemmings make up the majority of their diet. They hunt at night and during the day from perches where they listen intently for small mammals moving under the snow. Once they detect a small mammal they hover above the snow, and plunge talons first into the snow to grab it. Back to top

Nesting

Nest Placement

Nest TreeThese owls often choose a nest site near an opening in the forest, such as a meadow, bog, or field. The adults may visit a potential nest site two or more weeks before they settle on it. They often reuse the same nest site for several years.

Nest Description

Great Gray Owls don’t build nests. Instead they use old raptor or Common Raven nests, or even nests built by western gray squirrels, and do not add any additional material to the nest. They also place their eggs in the broken tops of dead trees, human-made platforms, or in clumps of mistletoe. If they nest in a broken-topped tree, the female may scratch a depression to lay the eggs, but she does not build a nest. The location where they lay their eggs varies depending on the nest site they chose to use.

Nesting Facts
Clutch Size:2-5 eggs
Egg Length:2.1-2.1 in (5.3-5.4 cm)
Egg Width:1.6-1.7 in (4.2-4.3 cm)
Incubation Period:28-36 days
Nestling Period:26-29 days
Egg Description:Dull white and unmarked.
Condition at Hatching:Helpless, eyes closed, completely covered in fluffy down.
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Behavior

Behavior Aerial Dive (ground/talons)Great Gray Owls are active at night and at dusk and dawn. They also hunt during the day, especially when they have nestlings or during the winter months. They forage in meadows where voles and other small mammals are abundant. In northern Europe, the Rocky Mountains, and the central Cascades of Oregon they also forage in clearcuts that have a few remaining trees for perching. They glide low over these open areas with slow and quiet wingbeats listening and looking for small mammals. They have excellent hearing and can find prey by hearing alone—even under a thick cover of snow—thanks to asymmetrical ear openings that help them triangulate sound with great precision. Males and females form pairs during the breeding season, but they don’t stay together during the nonbreeding season. Males and females defend their nest sites from other owls and raptors. The first line of defense is a threatening display. They spread their facial feathers to expose their bill, which they fiercely snap, drop their wings, or hoot to shun the intruder. If that doesn’t work, they may escalate territory defense to chasing and sometimes attacking the intruder. Most owls are year-round residents, but sometimes they move farther south in search of food. Populations in California and Oregon, in most winters, move to lower elevations areas with reduced snowpack. Back to top

Conservation

Conservation Low ConcernThe Great Gray Owl’s far northern range and elusive habits make it difficult to monitor population trends with surveys like the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population at 190,000, with 7% living in the U.S. and 43% in Canada (with the remainder occurring in Eurasia). The State of North America’s Birds 2016 report rates the species an 11 out of 20 on the Continental Concern Score and it is not on the 2016 State of North America's Birds Watch List. In the United States, Great Gray Owls are at the southern limits of their range and are uncommon, but they are fairly common throughout their Holarctic range. Back to top

Backyard Tips

If you are lucky enough to live within the range of the Great Gray Owl, you can build a nest structure to attract a breeding pair. Make sure you put it up well before breeding season. You'll find plans for building a nest structure of the appropriate size on our All About Birdhouses site.

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Credits

Bull, Evelyn L. and James R. Duncan. 1993. Great Gray Owl (Strix nebulosa), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

North American Bird Conservation Initiative. 2014. The State of the Birds 2014 Report. US Department of Interior, Washington, DC, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sibley, D. A. (2014). The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

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