Species Guide: Great Grey Owl (Strix nebulosa)
Family: Strigidae
The Great Grey Owl is a striking bird of prey found across the northern parts of the Northern Hemisphere. It is known for its remarkable size, distinctive facial features, and reclusive nature. Occurring in both North America and Eurasia, this species inhabits cold forested regions and plays an important role in its ecological communities.
Appearance
Male and Female
The adult Great Grey Owl is one of the tallest owls in the world, with a body length typically ranging from around 61 to 84 centimeters and a wingspan up to about 1.5 meters. The plumage of males and females is similar in overall gray and mottled brown patterning, with conspicuous concentric facial disks framing yellow eyes and a small, pale beak. Females tend to be slightly larger in body size than males, though there is no dramatic difference in coloration. Both sexes lack the prominent ear tufts seen in many other owl species.
Juvenile
Young Great Grey Owls resemble adults but often display slightly darker overall plumage that fades and becomes more defined as they mature. Juveniles also have large facial disks and yellow eyes, but their feathers can appear more uniformly gray or brown compared to adults.
Diet
Great Grey Owls primarily feed on small mammals, with voles and mice making up most of their diet. They detect prey by sound, including beneath deep snow, and swoop down silently to capture it with their sharp talons. Other food items can include shrews and occasionally small birds or amphibians, depending on local availability and environmental conditions.
Habitat
These owls favor dense boreal and coniferous forests, often near open spaces such as meadows, bogs, or muskegs that support abundant prey populations. Their range includes northern Alaska, Canada, and extends into parts of the northern United States, as well as across northern Eurasia. They rely on mature forest stands for roosting and nesting, especially where large trees and adjacent clearings provide hunting opportunities.
Behavior
Great Grey Owls are generally solitary and secretive. They are most active at night, dawn, and dusk, though they may also hunt during the day, particularly in the breeding season. They use a perch-hunting strategy, listening intently for prey before silently flying low over open areas to capture it.
Vocalizations
The typical call of an adult is composed of deep, evenly spaced hoots often repeated many times. Juveniles produce a variety of sounds, including chattering and shrieks, especially when begging for food.
Great Grey Owl Call:
Life Cycle
Breeding generally begins when individuals reach around two to three years of age. These owls do not build their own nests but use old nests of other large birds or natural tree cavities. Females lay between about two and five eggs in a clutch, with incubation by the female lasting roughly 28 to 36 days. After hatching, the young remain in the nest before learning to fly and eventually dispersing from the natal territory.
Biometrics1
| Length | 61-84 cm |
| Wing Span | 125-167 cm |
| Body Weight | 800-1300 grams |
| Longevity | 10-20 Years |
Natural Predators
Adult Great Grey Owls face predation pressures mainly from larger birds of prey such as great horned owls and northern goshawks. Raven harassment is also documented. Juveniles and eggs are vulnerable to a wider array of predators, including hawks, bears, pine martens, lynx, and eagles, particularly when nesting in accessible locations.
Relationship to Humans
Great Grey Owls hold a place in the cultural imagination of many northern communities, inspiring stories and local lore that highlight their mysterious presence in the forest. In some areas, they are associated with wisdom or forest spirits, and their rare sightings can draw bird-watchers from far afield. Their role in controlling rodent populations also contributes to ecological balance, which indirectly benefits human interests in forest and meadow ecosystems. Human disturbance and habitat modification, however, can negatively impact their populations by reducing suitable nesting and hunting grounds.
Conservation Status
The International Union for Conservation of Nature assesses the Great Grey Owl as a species of Least Concern at a global scale, reflecting its extensive distribution and relatively stable long-term numbers. However, regional assessments show variability: the species is considered vulnerable or sensitive in parts of the United States and subject to state-level conservation concern. In some states such as California, it is legally recognized as endangered due to habitat loss and fragmentation. Timber harvest and removal of large trees reduce nesting opportunities, while climate change projections suggest potential future reductions in suitable habitat.
California
Conservation Status
Global
Conservation Status
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References
- Lovette, I. et al. (2016) The Cornell Lab of Ornithology, handbook of bird biology. Third edition. Chichester: Wiley. [Accessed 23/12/2025]
CITATIONS
- Dunning, John B. Jr., ed. (1992). CRC Handbook of Avian Body Masses. Boca Raton: CRC Press. ISBN 978-0-8493-4258-5. [Accessed 23/12/2025] ↩︎
