Strix nebulosa
Unmistakable due to their sheer size, great gray owls are the largest North American owls in terms of size but not the heaviest. This honor goes to the snowy owl, which is on average at least 10 cm shorter in length and more than 1 kg heavier.
Great Gray Owl
Juvenile Great Gray Owl
Great Gray Owl in-flight hunting in a meadow
Great Gray Owl perched on the side of a tree
Portrait of a Great Gray Owl
Great gray owls are instantly recognizable and not easily confused with any other owl species, due to their extra large stature and distinctive facial patterning.
As their name suggests, their plumage consists of a large amount of gray, with white and brown patterning across the wings, back, belly, and breast. Wings are barred with lighter gray, darker gray, and some brown, with pale gray streaking, and the breast and belly have fine dark barring and are overall mottled with gray and brown. Their long tail is rounded and barred with brown, gray, and white.
The facial disc of a great gray owl is the largest of any owl species and features concentric gray and dark brown rings around the eyes, which are bright yellow and look relatively small, topped with strong white eyebrows. The bill is yellow, with a black patch immediately below, and a white collar is visible between the face and the neck.
Females and males are alike in plumage, but larger in all aspects than males.
Juvenile great gray owls are not as vividly marked as adults and have a more cryptic appearance, with mottled shades of gray and white, and develop a more adult-like plumage after 5 months.
Great Gray Owl adult
Juvenile Great Gray Owl
Great gray owls are undeniably large and powerful, but in terms of body mass, they trail behind the snowy owl and great horned owl, with much of their dense plumage accounting for much of their bulky size.
Female great gray owls are normally larger than males, and heavier too.
Great Gray Owl in-flight hunting in woodland
An evenly spaced series of whoo notes is used by both male and female great gray owls as a territorial call, with the male’s voice deeper in pitch than the female’s. Double hoots are used as a contact call between mates. A chattering cry is heard when the nest site is threatened or when intruders are sensed.
Great Gray Owl hooting from behind a tree
Small mammals are the primary prey of great gray owls, which are experts at catching rodents even when deep snow covers the ground.
Voles, pocket gophers, shrews, red and flying squirrels, mice, lemmings, weasels, and chipmunks are the most commonly caught prey. Birds are also taken but do not represent as important a share as mammals, with ducks, grouse, and songbirds.
Although most hunting is done during darkness, males may forage during the daytime in the breeding season to keep up with the demands of feeding hungry young.
Great gray owl chicks feed on whatever the male parent brings to the nest, which varies according to location but is frequently small voles, shrews, and pocket gophers. Initially, the female will shred the prey into pieces small enough for the young to swallow, but gradually young great gray owl chicks master the art of swallowing prey whole.
Great Gray Owl hunting during the winter months
Dense coniferous forests are the preferred habitat of great gray owls, particularly those that contain a mix of old-growth trees and younger plantations. Nearby meadows, marshes, and swamps offer important hunting grounds, as they normally have abundant populations of voles, mice, and other small mammals.
The primary range of great gray owls extends across the northern hemisphere, encompassing much of western, central, and southern Canada, parts of the northwestern US, and northern Eurasia, from Finland eastwards through Russia, Mongolia, and northeastern China.
In winter, occasional irruptions further south occur and nomadic wanderings may take some individuals outside of their regular breeding territories.
The overall global population of great gray owls is thought to be around 80,000 mature individuals, with around 38,000 of these resident in North America, and up to 19,900 in Europe.
Sightings of great gray owls are relatively uncommon, due to their nocturnal behavior, effectively camouflaged plumage, and preference for dense coniferous forests. However, they are not a particularly rare species and are widespread across forested landscapes of the northern hemisphere.
Montana’s Glacier National Park and the Bitterroot Valley are known for their great gray owl populations. Similarly, sightings are also regularly reported in Idaho’s Bitterroot Mountains and the Panhandle region. To the west, great gray owls are also occasionally spotted at Okanogan-Wenatchee National Forest, in Washington.
Great gray owls are widespread across much of western and central Canada, and a visit to any densely forested landscape in this region may reward you with a sighting.
The forests and meadows of Riding Mountain National Park in Manitoba offer a particularly decent chance of spotting a great gray owl. Ontario’s Algonquin Provincial Park is known for its diverse resident wildlife, including great gray owls.
Great Gray Owl in meadow landscape
First-time breeding is possible at one year of age, but rare. Young great gray owls usually breed for the first time at three years old, but occasionally will raise a successful brood at two years of age.
On average, the lifespan of a great gray owl in the wild is around 9 to 10 years, but individuals can live as long as 13 to 15 years, or in captivity for at least 27 years.
Great horned owls and ravens are both known to predate nests and take young birds. Great horned owls will also hunt adult great gray owls.
Great gray owls are included in CITES Appendix II, which legislates trade. In the US, the Migratory Bird Treaty Act of 1918 makes it illegal to kill, trap, injure, or trade great gray owls without a license. A similar law in Canada, the Migratory Birds Convention Act, offers the same level of protection to great gray owls in Canada.
Currently classed as a species of least concern, there are no immediate or current threats to the future survival of great gray owls, and their population is secure and increasing.
Great Gray Owl perching on top of a white fence
Unlike many other owl species, great gray owls do not nest in cavities, perhaps due to their vast size. Instead, they reuse old nest platforms abandoned by other birds that are bulky and strong enough to support them. The old nests of ospreys, ravens and goshawks - and even squirrels - are ideal.
Large snags – standing dead trees with broken tops – are also used. Nests are flat, to offer good visibility, and no additional material is added, although a depression is usually created by the female as a nest bowl before she starts laying.
In some regions, conservation projects are in place that aim to boost and manage populations of great gray owls, and artificial nest platforms have been introduced and successfully used to raise young.
Pairs form from early January onwards, and the important job of nest prospecting takes place over the course of three to four weeks before a final choice is made and eggs are laid. The peak months for eggs in North America are late March to early May.
Only female great gray owls incubate and are brought prey to the nest by their mate. Eggs hatch after 28 to 36 days, and young continue to be brooded in the nest by the female for a further two to three weeks. By between 26 and 29 days, young great gray owls are ready to fledge but continue to be fed outside of the nest by parents until they are around 3 months old.
Great gray owls’ eggs are a dull white in color, and slightly elongated. They measure around 5.4 cm (2.1 in) by 4.3 cm (1.7 in). A typical clutch consists of between 2 and 7 eggs.
Courtship begins as early as January, with males using ‘snow plunging’ displays to attract females at the start of the breeding season. Pairs remain together as they raise their young.
In some regions, pair bonds dissolve after young gain independence and become solitary and nomadic during winter months. In regions to the south, pairs remain bonded throughout the year but will seek a new mate if their original one dies.
Great Gray Owl sitting on the nest
A pair of Great Gray Owls at the nest with their young
Great gray owls have a reputation as being savage and fierce nest defenders and will strike with their razor-sharp talons at any potential predator that approaches too closely.
Intruders will be chased, and there are reports of humans sustaining slash injuries when they have disturbed a nesting great gray owl. Predators as large as bears have been driven away from nest sites by the vicious displays, and bill snapping and low hoots may be given as a warning to immediately precede an attack.
As a nocturnal species, great gray owls are active at night and sleep during the day, finding a spot close to the trunk where their plumage provides effective camouflage against the bark. In summer, spots near to the dense upper canopy are often chosen, offering relief from intense heat.
When raising young, male great gray owls may frequently hunt during the day too, to keep up with the feeding demands of their rapidly growing chicks.
Great Gray Owl in-flight in natural habitat
Great gray owls are usually resident birds, remaining in or close to their home territories for their entire lives. However, this can vary depending on prey availability.
Many great gray owls are nomadic, and wander from place to place outside of the breeding season and dispersing to regions with less snow cover in winter.
The main range of great gray owls lies to the north of the United States, although the southern extremes do extend across the border with Canada, and resident great gray owls are found across the northwestern states, through the Rocky Mountains, and as far south as the Sierra Nevada in California.
Great Gray Owl perching in the top of a tree
The global population of great gray owls is estimated at around 80,000 mature individuals or an overall population of approximately 120,000 individuals.
While great gray owls are North America’s largest owl species in terms of body length, they are not the world’s largest or heaviest owl.
Blakiston’s fish owl, resident in Russia, China, and the Japanese island of Hokkaido, is the world’s largest and heaviest owl, while in Europe, Asia, and Africa, the Eurasian eagle owl also eclipses the great gray owl in both length and weight.
Length:
61cm to 84cm
Wingspan:
137cm to 153cm
Weight:
700g to 1.7kg
Brighten up your inbox with our exclusive newsletter, enjoyed by thousands of people from around the world.
Your information will be used in accordance with Birdfact's privacy policy. You may opt out at any time.
© 2024 - Birdfact. All rights reserved. No part of this site may be reproduced without our written permission.
