Great Gray Owl

Great Gray Owl

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Description

The great gray owl is the tallest owl in Alaska, but not the heaviest (snowy owls are the heaviest). These owls are gray with large, yellow eyes.  Both the large size and absence of ear tufts are diagnostic features. They have a prominent white color on the front of the neck. The feathers on the chest and sides are 4-6 inches long and, when fluffed out, help keep the owl warm during long, cold winters. The bird has a naked patch under each wing to cool down during hot summers. The patch is usually hidden by the wings and adjacent feathers.  The owl has a distinctive facial disk, and the feathers of the disk help direct sound toward ear openings hidden by feathers. The skull is asymmetrical  with large bony cups surrounding the ear openings. These features help in detecting the nearly silent sounds of small rodents, as well as locating prey in the dark.

Lifestyle

The great gray owl is one of the most reclusive owls in North America. Although widely distributed in Alaska, it is common only in certain localities.  Along with secretive habits, this owl species is rarely seen and little known to Alaskans.  There is no evidence of this owl species migrating in Alaska, but they may move long distances when rodents are scarce.  Adaptations for hunting include the facial disk, soft feathers for silent flight, and the ability to turn the head three quarters of a circle (270 degrees). The feathers of the disk help direct sounds toward ear openings which are hidden by feathers. The owl also has an asymmetrical skull with large bony cups surrounding the ear openings.

Food Habits

This species hunts equally well both day and night, as they have excellent hearing and vision.  They hunt by perching on a tree overlooking a meadow or open area. Their hearing enables them to accurately determine the location of prey, even under two feet of snow or in tunnels. Once prey is located, the owl will silently glide from its perch and plunge into the snow to grab the rodent with talons.  In Alaska, their diet has been determined by analysis of regurgitated pellets, which contain undigested hair and bones. This revealed that small rodents were approximately 94% of the great gray diet, followed by shrews and birds.

Lifecycle

Great gray owls, like other owls, do not build nests but rely on old nests of hawks. They start visiting snow-covered nest sites in March. As spring approaches, males prepare for breeding and nesting season by performing aerial displays and bringing food to females.  Females lay one to nine white eggs in April or May, depending on how far the season has advanced. Eggs are incubated for about 30 days and usually hatch in June.  During years of low rodent numbers, great gray owls may not breed, and when they do, the number of eggs laid is related to food abundance. In years with enough food, the owls will tend to lay more eggs and more young will survive the nestling stage.  Owlets hatch covered with soft white down and their eyes open. Both parents feed the young by bringing food to the nest, tearing it into very small pieces that are eagerly consumed by the little ones. At three weeks of age and flightless, nestlings hop from the nest and climb on the nearby trees and shrubs.

Population Status, Threats & Conservation

This species is common only in select areas of Alaska and is seldom seen by people. The main factor that limits 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.  Their main predator is the great horned owl, although both of these birds are often harassed by ravens and other small birds.  The great gray owl is protected by both state and federal law, including under the Migratory Bird Treaty Act.  This species of owl is one of the most sought after by bird watchers.

Sources:
http://www.allaboutbirds.org/guide/great_gray_owl/id (Cornell)
http://animaldiversity.ummz.umich.edu/site/accounts/information/Strix_nebulosa.html (Animal Diversity Web)
http://www.adfg.alaska.gov/static/education/wns/great_gray_owl.pdf ADF&G