Bird of the Month: Great Gray Owl
Written by Andy McCormick
Andy McCormick, Volunteer and Former Board President of Eastside Audubon
The Great Gray Owl, named for its size and plumage color, is an owl that breeds around the world in the northern boreal forests.
The Great Gray Owl is North America’s largest owl by length but much of its bulk comes from layers of feathers which protect it from northern winters. The Great Horned Owl has a larger body mass (Bull and Duncan). The Great Gray is one of twenty-three of the world’s forest-dwelling owls which are placed in the genus Strix, which is Latin for owl. The Strix owls are medium to large size and do not have ear tufts. The Great Gray Owl, Spotted Owl (S. occidentalis), and Barred Owl (S. varia) are the three North American owls included in this genus. Nebulosa, the bird’s species name, is from the Latin describing an appearance like clouds, presumably referring to the Great Gray’s plumage (Holloway).
HUGE HEAD AND DISK FACE
The Great Gray Owl is distinctive with its very large round head and large facial disk accentuated with five dark concentric rings which make the yellow eyes seem small. The huge head gives this owl a front-heavy appearance in flight. In a frontal view, it seems to be wearing a black and white bow tie. Photos and video and the deep hooting call of the Great Gray Owl can be accessed at the Macaulay Library.
Often while perched on a low shrub, tree branch, or fence post, the Great Gray Owl appears to listen before attempting a capture. The bird’s wide facial disk gathers sound and aids this owl in locating rodent prey in grasslands. It has a slow and deliberate flight pattern and typically stays close to the ground. At times it will hover before making a sharp flip-turn as it pounces onto its prey. The Great Gray is also adept at capturing prey through the snow, and it has the strength to break through thick, crusted snow during a feet-first attack (Bull and Duncan).
Great Gray Owl
Scientific Name: Strix nebulosa
Length: 27”
Wingspan: 52”
Weight: 2.4lb (1,080 g)
AOU Alpha Code: GGOW
AN OWL OF MONTANE MEADOWS
The Great Gray is opportunistic in choosing a nest site. Most often it uses an abandoned nest of another large bird such as a raven or goshawk and some will use the top of a broken snag. It prefers to nest in dense coniferous forests but in an area that is close to its favored foraging habitat of an open meadow. A pair of Great Grays may use the same location for several years.
The female prepares the nest and alone incubates 2-5 eggs for about five weeks. Once hatched the nestlings are tended by the female for another 2-3 weeks. During these two months the male brings food to the female, which will eat some and distribute portions to the owlets. Once the young begin branching, they need care for another month or more before first flight. In some areas the female departs at this time, and the young stay with the male, which continues to bring food to them (Kaufman).
STATUS AND DISTRIBUTION
Bird Life International considers the Great Gray Owl a bird of Least Concern and has estimated the global population as stable but fluctuating between 50,000 and 100,00 individuals (Bull and Duncan). Fluctuations year to year are thought to be dependent on availability of rodents for nourishment. In years of lower rodent population Great Gray Owls can become irruptive and move southward and in doing so create much excitement among birders who love to see these owls which are rare in the lower 48 United States. Fortunately for Washington birders, there are breeding populations of Great Gray Owls in the Okanogan Highlands, the Blue Mountains, and in parts of the Cascade Range. Great Grays also follow the Cascades south through Oregon and into the northern Sierra Nevada in California.
In general, human threats to the Great Gray are minimal because the boreal forest habitat is away from most human activity, but cutting of old growth forests is a potential threat to these owls. Some human assistance has been provided in the form of nesting platforms which Great Grays readily use. Provision of this resource enables these owls to nest in areas without appropriate nest sites, and some of these owls have had a higher success rate on the platforms than on typical nests (Bull and Duncan).
Photo credit Mick Thompson. References available upon request from amccormick@eastsideaudubon.org.