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Great Gray Owls @ National Geographic Magazine
   
By Lynne WarrenPhotographs by Daniel J. Cox



Winged lords of northern forests, the big raptors fly noiselessly, hunt in light and dark, and can hear a field mouse stir under the snow.



These owls don't just pounce, they plunge. With ice-pick talons tucked under their chins, great grays hurtle headfirst into deep snow to snatch voles—diving with such power that they can shatter snow crust thick enough to hold a 180-pound person. They locate hidden prey with the help of large facial disks that funnel sound to their ears. When the plunge succeeds, as it did for this Manitoba owl, the hunter wriggles out of the snow then carries the prey to a safe spot for eating. This hunting technique gives great grays an advantage over other predatory birds, many of which must migrate to areas where lighter snows leave prey more accessible.

In winter adult great grays consume up to a third of their weight in rodents daily. Females in particular pack on reserves to sustain them through more competitive summer months. "It's as if there's a big winter sale on voles, and great gray owls are the only customers in the store," says Canadian conservation biologist Jim Duncan.

Researchers estimate that 20,000 to 100,000 great grays live in Canada and the U.S., with similar numbers in Europe and Asia. In North America, Duncan and his colleagues have found that northern populations of great grays are highly nomadic, flying hundreds of miles as vole numbers boom and crash in different areas.

By contrast, studies in Oregon and California have shown that more southerly populations, which have more diverse diets, tend to stay put, often occupying home ranges smaller than five miles across.
 
April in Montana: Snow is piling up, and the afternoon temperature won't make it above 25°F. With three owlets tucked snugly under her dense plumage—and a nearby mate that can continue to hunt by sound, however poor visibility becomes—this nesting female seems calmly prepared to ride out the storm. Great grays make devoted parents. Duncan has discovered that when prey is scarce, females will starve themselves—losing nearly a third of their body weight in a single month—so the maximum possible amount of food can go to their chicks. The return on this investment? Across North America 70 to 80 percent of great gray breeding pairs successfully fledge young.
 
Just big enough for mother and chicks, this 18-foot-tall Montana snag offers a commanding view of prime great gray habitat: mature forest with lots of flying room. Though adult great grays weigh only two to three pounds, they have wingspans 60 inches across and can be up to 33 inches high—by tape measure the tallest owls in North America. Their size makes it difficult for them to maneuver well in dense stands of trees. To hunt efficiently, they need meadows and other open spaces, often created by fire, wind, disease, or careful timber harvests.
 
Fluffy and feisty less than a month out of their shells (below), chicks don't stay nestbound long. As wastes accumulate, the area around the nest develops a smell that makes its location dangerously obvious to predators. So for safety's sake, chicks need to disperse even before they can fly; most owlets climb or tumble to the ground  when they're just three to four weeks old. Parents continue to feed and defend their brood through the summer. One in three great gray chicks is killed—by ravens, great horned owls, weasels, or other predators—or starves to death when its parents can't find enough prey to keep the family alive. Two-thirds survive until they're able to fly at seven to eight weeks old.

You're looking at a very aggressive bird," says Jim Duncan. When a great gray flares its facial feathers to expose the full length of its dagger-sharp beak, "it's like a snarling dog showing his fangs." From 30 feet away photographer Dan Cox used a remotely operated camera to record this adult patrolling the Montana clearing where its chicks were hiding. Parents attack anything—bear, lynx, unwary hiker—that gets too close to their young. What does a wallop from a great gray feel like? "Like being whacked by a two-by-four with nails sticking out of it," Duncan says.
 
When I first went looking for great gray owls in the Bridger Mountains near my home in Bozeman, Montana, I heard them hoo-hooing for days before I spotted one. Over several more summers I photographed what came to be a familiar group of birds hunting and raising young on the brushy slopes. A couple of seasons after I made this picture, I went back. The big trees were all gone, cut by a timber company. The owls were gone too; I didn't hear a single hoot. I know that natural and man-made disturbances open up vital hunting space for great grays. But along with good perches and plenty of rodents, these birds need big trees for nest sites. I was stunned, and sad. I wondered how far the owls had traveled to find new homes, and whether I'd ever see them on this mountain again.

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Flashback to the 1920s when an owl, complete with spinning head and glowing eyes, drew ice-cream customers from a Los Angeles roadside.



More to Explore

In More to Explore the National Geographic magazine team shares some of its best sources and other information. Special thanks to the Research Division.

Did You Know?
Spotting the Gray Ghost
Under normal conditions great gray owls are not found in Massachusetts. But when a great gray owl traveled south in 1973 to find prey, 3,000 bird lovers traveled to the state to see if they could spot it. Great grays are not easy to find, and their North American range is limited to Alaska, Canada, and a few northerly areas of the United States. If you don't want to wait until scarce resources send great grays south again, and if you are in the vicinity of La Grande, Oregon, chances are you can catch a glimpse of these owls from mid-May to early June. The Spring Creek area of the La Grande Ranger District is home to at least eight pairs of great grays that have been nesting there every year except one since 1982, in an area of four square miles (six square kilometers). For more information, call 503-963-7186.

—Michelle R. Harris
Did You Know?

Related Links
Owl Pages
www.owlpages.com/species/strix/nebulosa/Default.htm
Visit the owl pages to read a general overview of the great gray owl and listen to its calls. From here you can fly with owls all over the world.
 
Owling.com
www.owling.com/GGO_nh.htm
Explore another good site to check out an overview of the great gray owl.
 
The University of Minnesota's Raptor Center
www.ahc.umn.edu/ahc_content/colleges/vetmed/Depts_and_Centers/Raptor_Center/index.cfm
Search for the great gray owl from the Raptor Center's main site. Not only can you find out about other raptors, you can even watch an owl use its second eyelid.
 
La Grande Ranger District and the Wallowa-Whitman National Forest
www.fs.fed.us/r6/w-w/about/lgrd.shtml
For information on this owl territory in Oregon, look here.

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Bibliography
Bull, Evelyn L., and Mark G. Henjum. "Ecology of the Great Gray Owl." U.S. Forest Service general technical report PNW-GTR-265 (September 1990).
 
Bull, Evelyn L., and James R. Duncan. "Great Gray Owls." The Birds of North America (1993), 1-15.
 
Court, Gordon. "Winter Grays." Natural History (Feb 1998), 50.
 
Duncan, James R. Owls of the World: Their Lives, Behavior and Survival. Firefly Books, 2003.
 
Eckert, Allan W. The Owls of North America (North of Mexico). Weathervane Books, 1987.
 
Hume, Rob. Owls of the World. Running Press, 1991.
 
Johnsgard, Paul A. North American Owls: Second Edition. Smithsonian Institution Press, 2002.
 
Voous, Karel H. Owls of the Northern Hemisphere. MIT Press, 1988.

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NGS Resources
Warren, Lynne. "Muscle & Magic: Snowy Owls." National Geographic (December 2002), 104-19.
 
Field Guide to the Birds of North America, 4th ed. National Geographic Society, 2002.
 
Spines, Christine. "The Magic of the New Movie: Harry Potter and the Sorcerer's Stone." National Geographic World (November 2001), 12-16.
 
Mitchell, John G. "Oil on Ice: Economic Boon, Environmental Disruption—Alaska Weighs the Problem." National Geographic (April 1997), 104-31.
 
Dekin, Albert A., Jr. "Sealed in Time: Ice Entombs an Eskimo Family for Five Centuries." National Geographic (June 1987), 824-36.
 
"Peoples of the Arctic." Supplement map, National Geographic (February 1983).

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