The Great Gray Owl (Strix nebulosa) is a very large nocturnal bird of northern (mainly coniferous) forests and wooded bogs as well as some high mountain meadows in western North America. Great Gray Owls are resident across much of boreal Canada and Alaska and in Eurasia from northern Scandinavia, northern Russia, and northern Siberia south to central Russia, northern Mongolia, and northern Manchuria., Amurland, and Sakhalin. where they are most often found near bogs, along forest edges overlooking fields, in mountain meadows, and around cultivated land, airports, and roadsides.

The Great Gray Owl is distinctly larger than the Great Horned Owl and Snowy Owl and much larger than the Barred Owl (although a surprising proportion of its bulk consists of feathers rather than bones and muscle). Its flat face is punctuated by small yellow eyes surrounded by concentric rings. Although Great Gray Owls are most active at dawn, at dusk, and at night, they hunt during daylight in summer (and in winter if food-stressed), although still generally near dawn or dusk. Wingbeats are deep and slow. Both sexes produce a call consisting of 5 to 10 very quiet (typically inaudible beyond 400 m) evenly spaced deep hoots at a rate of around one per second.

The diet of the Great Gray Owl consists mainly of small mammals, especially Microtus voles. These owls can detect prey under snow by sound and can plunge and break through snow crust hard enough to support 80 kg and as deep as 45 cm. Small mammals are swallowed whole and larger prey are pulled apart. Abandoned nests of other large bird such as Goshawks, Ravens, or Ospreys 10 to 50 feet above the ground are the most common nest sites, although these owls may sometimes nest on top of broken tree trunks and, rarely, on the ground; nests may be reused for several years. Typical clutch size is 2 to 5 eggs (clutch size may be larger in years with abundant food). Incubation (for 28 to 36 days) is by the female only, but the male brings food to the incubating female on nest. The female broods young for their first 2 to 3 weeks. In some areas, the adult female departs after young fledge while the male remains and feeds them for up to 3 months. In some winters, large numbers of Great Gray Owls may move south or southeast into eastern Canada and the extreme northeastern United States in North America and northern Germany and Ukraine in Europe (apparently in response to a sudden drop of rodent population). Great Gray Owls may live more than 20 years.

(Kaufman 1996; Dunne 2006; Svensson 2009; AOU 1998; Holt et al. 1999 and references therein)

Strix nebulosa resides in Alaska, Canada, the higher elevations of the Rocky Mountain States, northern Minnesota and northern Wisconsin. Also, S. nebulosa breeds from northern Yukon to northern Manitoba and northern Ontario, south locally to central California, northern Idaho, northwestern Wyoming, central Saskatchewan, northern Minnesota, and south central Ontario. Winters generally through the breeding range, wandering south irregularly to the northern tier of States. It also occurs widely across Europe and Asia. (Osborne 2001, UNEP World Conservation Monitoring Center 2001).

Biogeographic Regions: nearctic (Native ); palearctic (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: BREEDS: central Alaska to northern Ontario, south locally in mountains to California (vicinity of Yosemite), Idaho, Montana, Wyoming, central Saskatchewan, northern Minnesota, and south-central Ontario. WINTERS: generally throughout breeding range, wandering south irregularly to northern U.S. Also in Old World. Usually uncommon, but sometimes may be locally abundant.

The Great Gray Owl is the tallest owl in Alaska standing at a length 24-33 inches high, with a wing span of 54-60 inches, depending on degree of maturity. Strix nebulosa is larger and grayer than other owls and its round head does not have any ear tufts. Its bill and eyes yellow.

The owl has a distinctive facial disk, with two obvious gray concentric circles. The feathers of the disk help direct sounds toward the ear openings that are hidden by feathers. The owl also has an asymmetrical skull with large bony cups surrounding the ear openings.

In addition to the predominately gray plumage and distinctive facial disk, the bird has a black chin spot just above two white-feathered mustaches and it has a prominent white collar on the front of the neck. Ventrally, the owl is exhibits varying shades of dark and light grays, browns, and white. The dorsal side has a little less white than the ventral side. The tail is long and extends beyond the folded wings.

Adaptations for hunting include the facial disk, soft feathers so flight is silent, and the ability to turn its head three quarters of a circle (270 degrees).

(The Owl Pages; Compton's Encyclopedia 1998; MacBride Raptor Project 1997; Baetsen 2000; Wolf 2000).

Range mass: 790 to 1454 g.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Length: 69 cm

Weight: 1298 grams

Systems

• Terrestrial
• Freshwater

In North America, Strix nebulosa inhabits dense coniferous forests in Canada, and montane coniferous forests of the western States. It usually prefers pine and fir forests, rarely straying far out onto tundra barrens and muskeg marshes. Nests in mature poplar woodlands, well secluded from human activities, and in spruce stands with islands of tamarack. In winter, it may inhabit forests, sparse woodland edges bordering open fields, weedy fields with posts or scattered low trees or bushes, or brackish tidal meadows (Baetsen 2000; The Owl Pages).

Terrestrial Biomes: tundra ; forest ; mountains

Comments: Dense coniferous and hardwood forest, especially pine, spruce, paper birch, poplar; also second growth, especially near water, foraging in wet meadows; boreal forest and spruce-tamarack bogs in far north, coniferous forest and meadows in mountains.

Nests in top of large broken-off tree trunks (especially in south), in old nests of other large birds (e.g., hawk nest) (especially in north), or in debris platforms from dwarf mistletoe; frequently near bogs or clearings. Nests frequently reused (Franklin 1988). Same pair often nests in same area in successive years.

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Greater mobility exhibited in years when food scarce (Duncan 1987). Food scarcity or unavailability may cause post-breeding movement upslope and downslope movement in winter (California Department of Fish and Game 1990). May move several hundred km southward for winter; in some areas, longest movements made by immatures (but see ECOLCOM).

In the wild, Strix nebulosa feeds primarily on small rodents such as voles and pocket gophers. Small rodents composed 80-90% percent of the diet while other mammals (mainly shrews) and birds composed the remainder (The Owl Pages).

The Great Gray Owl hunts by perching on a tree overlooking a meadow or open area. The owl's keen hearing enables it to accurately determine the location of its prey, even under two feet of snow or in tunnels. Once the owl locates some food, it silently glides from its perch and plunges into the snow to grab the rodent with its sharp talons. Fresh "plunge marks" will occasionally show an imprint of the owl's outstretched wing feathers where the owl dropped into the snow. In many areas these marks are often the only indication that Great Gray Owls are in the area (MacBride Raptor Project, Wolf 2000, Baetsen 2000).

Comments: Diet in North America dominated by pocket gophers and voles. Forages usually in open area where scattered trees or forest margin provides suitable sites for visual searching; also uses sound to locate prey under snow cover.

Strix nebulosa preys on:
Parascalops breweri
Microtus xanthognathus

This list may not be complete but is based on published studies.

10,000 to >1,000,000 individuals

Comments: Guesstimated number of breeding pairs in Canada in the early 1990s was 10,000-25,000 (Kirk et al. 1995). See Johnsgard (1988) for listing of recent status studies in Manitoba, Saskatchewan, California (about 10 breeding pairs, California Department of Fish and Game 1990), Wyoming, Idaho, and Oregon.

Some may remain on breeding territory all year; others may move irregularly in search of favorable foraging conditions. In Oregon, radio-tagged juveniles moved 9-31 km from nest over period of 1 year, adults moved 3-43 km during same period (see Johnsgard 1988). Predation by great horned owl was greatest known mortality factor in northern Minnesota and southeastern Manitoba (Duncan 1987).

Comments: In winter, hunts primarily in early morning and from late afternoon until dusk. When nesting, may hunt day or night.

Average lifespan

Status: wild: 153 months.

Maximum longevity: 15.8 years (wild)

Breeding takes place in late winter with the pair generally utilizing an abandoned hawk or crow's nest. The female Strix nebulosa lays eggs in March- June, depending on temperature range (egg laying may be delayed in deep snow years). Two to five dull white oval eggs are laid and are incubated by the female Strix nebulosa for a period of 28-29 days. The owlets hatch covered by soft white down with their eyes open. Both parents feed the young by bringing food to the nest, tearing into very small pieces that are eagerly consumed by the little ones. Soon the down begins to disappear and is replaced by feathers. Once the owlets are 'feathered out' they begin the pre-flight exercises. They can be observed walking around the top of their nest flapping their wings and gripping the nest edge with their talons. Young leave nest after three to four weeks with the ability to climb well. (The Owl Pages).

Average time to hatching: 30 days.

Average eggs per season: 2.

Egg dates: late March-May in Alberta, late April-early June in Ontario, peak mid-April to late May in California, mean date of first egg 5 May in southern Idaho and northwestern Wyoming; eggs laying may be delayed in years with deep snow (Franklin 1988). Clutch size is 2-5 (usually 2-3 or 3-4). Incubation lasts 28-29 days, by female (male brings food). Young begin to leave nest at 3-4 weeks (4 weeks in Idaho/Wyoming), fly well at 5-6 weeks (6 weeks in Idaho/Wyoming), independent at about 4-5 months (Idaho/Wyoming: Franklin 1988). Usually first breeds at 3-4 years. Pair bond is not maintained outside breeding season, but bond may reform if both birds return to the same breeding territory. Some pairs may not breed in years of low prey abundance.

The following is a representative barcode sequence, the centroid of all available sequences for this species. 

 
There are 8 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
 

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 8
Species: 8
Species With Barcodes: 1

The U. S. Department of Interior Bureau of Land Management considers Strix nebulosa to be a sensitive species, and it is protected in the United States on both federal and state levels. It has been the subject of extensive management studies (Huff et al. 1997)

The Great Gray Owl is rarely seen by people and is very vulnerable to human disturbance such as clearing of forests for timber or farming. The main limit to its distribution is the availability of nest sites. If there are sufficient nest sites, then other factors such as food supply, determine how many owls live in the area. Chemicals used in exterminating mice and other pests have detrimentally affected the food chain of Strix nebulosa 

Wildfires can increase the availability of nest sites by creating suitable stumps, and they can also increase mouse populations.

(Idaho Conservation Data Center 2001, Huff et. al 1997, Mann,

Osborne 2000).

US Migratory Bird Act: protected

US Federal List: no special status

CITES: appendix ii

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Large circumboreal range; no decline is evident in the vast majority of the range, but few data are available for most areas.

Comments: In California, habitat loss through logging of mature forest and overgrazing of meadows has been the primary cause for decline (California Department of Fish and Game 1990).

Management Requirements: In addition to the provision of suitable habitat, management needs include protection of nesting areas from excessive human activity during the nesting season. For the Pacific Northwest, U.S. Forest Service et al. (1993) and Thomas et al. (1993) recommended providing a no-harvest buffer of 300 feet around meadows and natural openings and establishment of a 1/4-mile protection zone around known nest sites.

Artificial nest platforms have been used successfully (Bull et al. 1987, California Department of Fish and Game 1990).

The restrictions enforced on the logging industry because of the threatened status, will most likely be costly, and will potentially set back any business that relies on these resources for lumber and wood products. (Mann)

Strix nebulosa is important in the ecological balance; they scavenge and dispose of carrion and provide a check on rodent populations. Also, this rare owl draws many bird-watchers from everywhere. In Alaska, Athabaskans may use it as a food source due to its stored winter fat.(Compton's Encyclopedia 1998; Osborne 2000).