GREAT GRAY OWL
TOP 5 ID TIPS: GREAT GRAY OWLS
Very large bird
Dark grey, light grey, and brown pattern
Broad, flat, and very defined facial discs
Usually very quiet, silent when flying
© Kurt Lindsay
GREAT GRAY OWL APPEARANCE
The Great Gray Owl has charmed millions of birders worldwide with its unique appearance - sometimes described as looking surprised or frowning with a bowtie plumage patch below its chin. Even those living outside this bird’s northern hemisphere range have fallen for them. In fact, so many adore these birds that a lone Great Gray Owl in Massachusetts attracted over 3,000 birders in less than two months.
As the tallest North American owl, the Great Gray stands up to 33 inches tall. However, much of this species’ height is made up of puffy feathers, which protect them from harsh winter conditions. They may appear larger because of their height, but the Great Gray Owl’s body mass is generally 25 -50% less than that of the Great Horned Owl. Great Horned Owls can weigh up to 4-pounds, while a Great Gray averages only two-to-three pounds. Since the Great Gray Owl is smaller than many of its neighboring raptor species, they can be prone to getting picked and preyed on by larger, more aggressive birds.
© Kurt Lindsay
© Kurt Lindsay
GREAT GRAY OWL HUNTING
Great Gray Owls are powerful hunters who have adapted to hunt rodents in cold, northern climates. Perching on a branch with a cocked head, the Great Gray listens for tunneling rodents beneath deep snow. Its incredible hearing allows them to detect prey over 320 feet away. A Great Gray Owl can even plunge through snow as deep as 17 inches, even plunging through snow crusts
able to support a 175-pound person in order to catch a meal. In the summer, Great Gray Owls have been known to dive to the ground, breaking through loose soil to grab small mammals in shallow burrows. These impressive seasonal hunting techniques
allow the Great Gray Owl to feast on its favorite meal year-round: rodents!
GREAT GRAY OWL NESTING
© Kurt Lindsay
Come springtime, the female Great Gray Owl is ferocious in protecting her nest. One female was even seen chasing a full-grown Black Bear from her nest site! In most cases, however, females vocalize and perform distraction displays to draw attention away from the young in the presence of a threat. So protective are some female Great Grays that field researchers sometimes use face masks and helmets to protect themselves while conducting research.
Despite the Great Gray Owl’s popularity throughout the
world, this bird still faces a variety of threats. Competition for suitable nest sites is often severe between the Great Gray and other raptors. Broken tops of large-diameter dead trees, or snags, are their preferred nest sites, as they accommodate the owls’ large size. Unfortunately, suitable snags are a limited resource; they are often cut for firewood, removed for safety by forest managers, or fall down naturally. These factors sometimes leave Great Gray Owls virtually homeless come nesting time.
© Kurt Lindsay
Other threats include predation by larger raptors, starvation, collisions with automobiles and powerlines, and shooting. Young Great Grays may face health issues brought on by the bites of black flies, including swelling of the eyelids and death.
© Hendrick Bosch
GREAT GRAY OWL CLIMATE
With such thick, fluffy feathers, Great Gray Owls are well-equipped for the cold winter months in their Northern habitats. However, the warm summer months of Montana, Canada, and other areas can quite uncomfortable for these owls. These warm feathers trap hot air next to the owl’s skin, making heat stroke a risk when it’s hot and humid in the summertime. Montana’s summer days sometimes reach 100-110°F, a miserable temperature for Great Gray Owls. Although they may find relief at higher elevations, near water, or beneath the canopies of forests, there is one way these birds can cool off. By holding or “drooping” their wings outward, fresh, cooler air can filter into the owl’s feathers, cooling the skin and blood beneath it. Great Gray Owls have also been known to “gape” when overheated, somewhat like a dog would pant.
This photo from Hendrik Boesch shows a Great Gray Owl both gaping and drooping its wings.
GREAT GRAY OWL RESEARCH
We are excited to have a research project up and running on Great Gray Owls. Similar to our other owl projects, we will be conducting long-term monitoring of nest sites, banding, collecting data, and surveying new areas. In conjunction to our base study, we are also interested in learning more about their nest requirements. Similar to cavity nesting owls, Great Gray Owls depend on very specific site characteristics in order to nest. While obligate cavity nesters need to find the holes of woodpeckers, natural tree holes, or nest boxes; Great Grays look to large, broken-topped trees, and abandoned stick nests of other large birds. The owls nest on the top of the snag where the tree has broken and, due to the owls' massive size, trees have to be large enough to accommodate them.
A special focus of our Great Gray project is to record the measurements of successful nesting sites. In doing so, we can develop a predictable model for identifying suitable snags. This data will be passed on to forest managers who can make decisions to preserve and manage for these trees.
© Hendrik Bosch
GREAT GRAY OWL FACTS:
A large, grayish-brown owl with a big, round head
Males: greyish-brown with grayish mottling and barring; face is light gray with several dark rings on the facial disks; bright yellow eyes and beak
Females: similar to male
Young: more gray; fades to brown with age
Dark Wood Owl, Lapland Owl, Striped Owl, Lapp Striped Owl
Ural Owl, Barred Owl
GREAT GRAY OWL SIZE:
Height: Males 61-84 cm (24.0-33.0 in), Females 61-84 cm (24.0-33.0 in)
Weight: Males 890g (2.0 lb), Females 1267g (2.8 lb)
Wingspan Both: 137-153 cm (53.9-60.2 in)
GREAT GRAY OWL RANGE:
A northern owl; ranges throughout interior Alaska, Canada, northern U.S. Rockies, and a few scattered locations further south
GREAT GRAY OWL HABITAT:
Dense boreal and coniferous forests, often adjoining open areas like bogs, muskegs, or meadows
GREAT GRAY OWL DIET:
Small mammals such as voles and mice; shrews; rarely birds
GREAT GRAY OWL VOICE:
Deep, booming hoots
Males: during breeding, a series of evenly spaced low pitched “hoo”s; to contact other owls or defend territory, often will give a soft, double hoot
Females: higher pitched than males
GREAT GRAY OWL NESTING:
Nest Site: abandoned nests of other raptors, broken tops of snags, or artificial nest platforms
Eggs: 2-9, depending on availability of food; usually 3-5, hatching asynchronously
Incubation: 28-36 days
GREAT GRAY OWL HUNTING HABITS:
Usually hunts from a perch where it attentively listens and watches for prey
GREAT GRAY OWL CONSERVATION STATUS:
Not globally threatened, but sensitive in U.S. and vulnerable in Canada.
ALSO OF INTEREST:
• Closely related to the Barred Owl (Strix varia)
• May be residents of an area or nomadic
• Migration based on prey availability
• Uses mostly montane meadows for hunting
• Not found in North American fossil records
• Ears highly adapted and feet/talons small compared to
• May have unusual ability to withstand starvation
• Perhaps sensitive to summer heat because of thick plumage
• Male uses pseudo-hunting and excessive snow dives in
• Usually don’t breed until three years of age
• Young have only an estimated 63% chance of survival from egg phase to first flight; 51% chance of surviving first year of life; and 31% chance of surviving the first two years of life.
• To keep the nest clean, females typically consume the
feces and pellets of young up to a week before they fledge.
• Great Gray Owl’s long legs have warm insulating feathers to protect from frostbite and feisty prey animals
GREAT GRAY OWL DISTRIBUTION IN NORTH AMERICA
Maps provided by The Birds of North America Online and the Cornell Lab of Ornithology.
Small creatures of the North beware; the Great Gray Owl is on the hunt! From atop its perch, this enormous owl- the largest in North America- is waiting…waiting for the chance to strike. Cocking its head as it listens for the tunneling of rodents beneath deep snow, the Great Gray Owl, with its incredible hearing, can detect prey over 100 meters away through snow as deep as 45 centimeters. When prey is heard, the Great Gray will leave its perch in one fast swoop, diving down through even the heaviest of snow to find a meal. It will most likely resurface with a shrew or vole grasped in its talons. Great Gray Owls also hunt larger prey like Snowshoe Hares, and has even been known to kill birds as large as the Sharp-shinned Hawk. Watch out northern critters; there’s no hiding from the Great Gray hunting machine!
© Kurt Lindsay
Owl Research Institute
Birdsna.org by Cornell Lab of Ornithology
Edited and arranged by Brooklin Hunt, VA, ORI Intern 2017-18