Species profile: Denizen of the northern forests, Great Gray Owl
One researcher's account of the Great Gray Owl
Published: September 1, 1988
|Mid-February late afternoon, overcast, calm — a good day to be out looking for owls. We drive around a bend in a small road and see two Great Gray Owls, one on a roadside fencepost, the other in a tree. The fencepost owl ignores us, in spite of our close approach. It steadily watches the other owl. What's going on here? Over the fence we go, through deep snow toward the second owl, but it too ignores our trapping efforts.|
Frustrated by the lack of response from both birds, we stand puffing in the cold, then hold our breaths, transfixed, as the fence owl slowly flies out over the snow, 50 feet in front of us. It flaps heavily with fully outstretched wings, hovers — a gigantic moth in slow motion — ¬floating a dozen feet above the snow, then raises its wings in a V, tips forward and plunges into the snow. Seconds later it sits upright, a great, dark cat-like figure. It is courtship! These owls have no interest in the two men standing between them, mired in waist-deep snow; they are playing out their own game.
The male repeats his spectacular performance a dozen times, flying back to the fence and out over the field again, his display an exaggerated pattern of normal hunting behavior. The beauty and solemnity of the male's effort to do the impossible, to hang in mid-air, is overwhelming. It all ends when the male flies to the female in the tree. At once she dashes aggressively at him, striking him, then away she goes, darting through the trees, followed by her persistent suitor.
Big, bold, and beautiful, the Great Gray Owl attracts much attention wherever it is found within its circumpolar range. This denizen of the northern forests, with its commanding presence and dismaying disregard for mankind, is our largest North American owl.
For many birders the only opportunity to see a Great Gray Owl is in winter in those years when owls appear outside their breeding range in southern Ontario and Quebec and the northeastern United States. Even near known breeding areas in Alberta, Wyoming, Minnesota, and Manitoba, winter is when the bird is most often seen.
Every winter since 1968-69 my longstanding friend and colleague, Herb Copland, and I have gone out looking for Great Gray Owls to capture and band. One memorable year we tallied an incredible 88 owls. It's an exciting pastime, combining science with sport. Over the past 20 years we've seen a lot of owls, sometimes watching them hunt for long periods. The owl's attitudes as it looks and listens for small mammals, the graceful flight and sudden strike, reveal much of the nature of this efficient raptor.
Courtship displays in birds often are derived from maintenance behavior patterns like nest-building, feeding young, and searching for food. The Great Gray Owl display described above derives from a common technique used by Great Grays to obtain prey from under snow. These birds can hear a vole a hundred feet away and under more than a foot of snow. The owl flies out to the concealed prey, hovers above it to get a better fix, then plunges head downward into the snow like a tern diving into water. With its long, powerful legs it can thus grab a mouse 18 inches below the surface. This behavior is an adaptation for obtaining prey living beneath the deep snow of the boreal forest, and it is not surprising that it should have become part of the ritual of courtship.
Long before winter is over, Great Gray Owls are inspecting nests and setting up territories. Adapted to nesting in the tops of snags and in old hawk-nests, Great Gray Owls have been successfully attracted to nest in man-made structures. The earliest case appears to have been a nesting in 1974 in a stick-nest we built four years earlier just over the border in Minnesota's Roseau Bog. Since then, Great Grays have nested in structures built for them in Alaska, Oregon, California, Idaho, Ontario, Minnesota, Manitoba, and Wisconsin. Often, at least in the western states, simply preparing a large snag by sawing off a portion of the top of a tree, then hollowing it out, suffices. Biologists with the U.S. Forest Service in Oregon have had good success with shallow wooden boxes fastened high up on the trunks of large trees. In 1987, Great Gray Owls occupied about three dozen of our nest-structures in southeast Manitoba and adjacent Minnesota. Man-made nests provide a way to determine whether Great Gray Owls occur and breed in an area. They can help increase the number of breeding owls in a given area, and they help provide access to breeding birds for study, photography, and, perhaps, viewing. But provision of man-made nests, except in very limited sites, is scarcely a substitute for natural nests.
The welfare of the Great Gray Owl, over much of its range, depends on hawks that share its habitat. Because these owls do not build their own nests, they rely on other species for nest sites. Should there be a failure in the populations of such birds as the Northern Goshawk, Red-tailed Hawk, Broad-winged Hawk, and, perhaps, the Common Raven, it is certain that the Great Gray Owl could not long maintain itself. Thus, at least two things are required to ensure healthy numbers of owls: good populations of hawks and mature or large, deformed trees to support hawk nests. This leads one to conclude that maintenance of tracts of old forest, or at least stands including some mature trees, is a basic requirement for ensuring the future of the Great Gray Owl. Old forest provides additional nesting sites, for when older trees are toppled by the wind, snags may be left in which these adaptable owls can lay their eggs.
Raptors, like most birds, tend to flee when approached. But at the nest they become different birds. Once a Great Gray Owl has laid her first egg, she is locked into a pattern of attentiveness. The male brings her food, while she takes few breaks and does all of the incubating. For a month and a half, a Great Gray will incubate her clutch of three to five or more eggs. Day after day throughout this period we find her on the nest, supine, head upright, watchful. She becomes one with the nest and the tree, swaying in the breeze, exposed to sun, rain, and wind. It is a glorious sight, and a privilege to witness. Now we can mark her day, watch her carefully following the flight of a hawk soaring far overhead, see her blink at the chatter of an inquiring jay. A month later, with the hatching of the first egg, there is increased activity at the nest. That first peeping of her offspring may even be heard from within the egg. The new voice causes a change in her behavior. Bracing her feet, she turns her face downward to inspect the newcomer, gently nuzzling the chick with her bill. One wants to shout with glee for her, but it is a time to be silent.
At the end of one long day in April 1987, after a colleague and I had visited 17 nests, seven of which were occupied by Great Grays, I went back alone to spend an hour beside one of the nests. It was a pleasant, cool evening, no mosquitoes and strangely quiet. From the nest, 20 feet above me, the incubating female's eyes followed my every move. Sitting on a mossy hummock and leaning against a nearby tree, I pondered the circumstances that brought the pair to this particular nest. How do owls find our nests? This is something we know little about. Presumably the male — if it is the male who seeks out nests — has some kind of search pattern. An ability to remember the location of nests encountered while flying by or during active search would seem necessary. Though perhaps not as wise as the folktales would have us believe, owls, like other birds, have good memory and are quick to learn.
Bob Taylor, a nature photographer who has spent many hours photographing Great Gray Owls at their nests, maintains that this is the best way to get to know the species. After he spent several days in a blind at a nest in May 1987, I asked him if he'd seen anything new.
"It isn't so much that there's anything new," he replied. "It mostly reaffirms what I've felt before. Sitting for up to 14 hours a day in silence at an owl's nest, one becomes part of the woods. The owls hold one's attention — the mother, the downy young, the male bringing food. But there's a lot more. There's time to notice the tender tamarack needles coming out, purple tamarack cones, bunchberry leaves in rosettes against the moss and lichen covering the forest floor. And the birds! At this season, especially early in the morning, they're all singing — warblers, Nashville, Connecticut, Tennessee, and Yellow-rumped ... and the Ruby-crowned Kinglet, Winter Wren, Brown Creeper, White-throated Sparrow, and others.
"But I did see something new. Two large, downy young lay in the nest. The female was perched about 30 feet away, keeping quiet vigil. The male came flying in over the treetops, carrying a vole, heading straight for the nest. Suddenly, the female called, and on her signal the male braked in mid-air and dropped straight down about 12 feet to land right beside her. It was terrific!"
Steve Loch, another nest-builder, has been studying owls for several years in north-central Minnesota, where he discovered a large breeding population. We have worked closely together. Loch's idea of a good time is to run through a tamarack bog to capture and radio-mark a juvenile owl. Renate Scriven, a young friend of mine who assisted Loch for a few days, told me that they pursued one owl for five and a half hours before they caught it, leaping over deadfalls and splashing through the bog, trying to keep it in sight each time it flew.
Late one evening, Loch and I tried to capture an elusive adult female Great Gray by attempting to lure her close. For three frustrating hours, we persisted. She perched high and out of reach. None of the magic seemed to work, but at least the Brittany spaniel we brought along to help attract her was having a good time. As the night descended, there was a moment of hushed stillness; I felt safe though I was aware that in the growing darkness the trail out was fading. I watched with glee when a Whip-poor-will darted past, feeling comforted by the surrounding banks of trees and lighter patches where sedge meadows rustled with mice. I stood still to watch the owl, calmly letting willow leaves tickle my cheek, too uncaring to move, my palm braced against the prickly bark of a tamarack, the scent of old moss and decayed wood a pleasant reminder of other bogs, other times. Wet feet and stinging, nicked shins told me where I stood in this strange, lovely world where we pursue mad dreams... The dog and I stood close together watching Loch make one more effort to snare this oh-so-wary bird perched high atop a spruce, a silhouette at this late hour, the object of our quest.
At Loch's suggestion we backed off to give the owl time to relax, thinking she might change her pattern of behavior and drop her wary spirit. Within the edge of the spruce we found a log, made ourselves comfortable, and waited, mosquitoes by now hovering about us in little clouds. The bond between us was strengthened when Loch quietly admitted this was the first time he had felt relaxed and at ease for months. It is curious, where there should be frustration there is quiet acceptance. When our evening ended, when finally we gave up, it was on a note of gratitude for the time we'd spent in this little wilderness.
The dog led us out, making graceful leaps over fallen logs across the murky trail, while I stumbled along, catching my breath and wincing when sore toes complained. On the road I staggered a bit and spotted the distant car with relief. It was 2:30 a.m. when I rolled into my driveway. The house lights were all on, and my wife and son stood in the driveway looking restless and worried. They were worried about the dog.
While I told them my stories, we picked ticks off the dog. I went back into the bog the next morning with a numb wonder at the drive that compels me to return to these strange owls and their haunts. It was with some relief that I went to the office the following Monday, limping down the hallways, immersing myself in other tasks and other people and a lot of indecision and fretfulness. In odd moments I recall the time in the bog and am reassured.
During winters with deep snow and severely low temperatures one can expect to find Great Gray Owls in Manitoba, especially on calm, overcast days. The best places to look are along roads in or near the Provincial Forests east of Winnipeg and south of Lake Winnipeg. Retiring by nature, and fond of deep woods, hunger brings Great Grays out into the open. Usually, they find sufficient prey within the forest, but following rodent declines, especially following a high production of young owls, they may be forced to move many miles in search of food. In some years, these movements outside the usual range involve large numbers in what are called irruptions or invasions.
One of the largest Great Gray Owl irruptions in northeastern North America occurred in winter 1978-79, when an estimated 334 birds were recorded. The close relationship between owls and voles was well demonstrated that winter by the numbers of birds foraging for meadow voles on an island off the north shore of Lake Ontario. Amherst Island is only 25 acres in size, but 10 species of owls were recorded, including 18 Great Gray Owls. Startled observers one day found nine Great Grays perched at the same time in a single large elm tree!
Great Gray Research Fund
The Manitoba study of the Great Gray Owl is being conducted under the auspices of the Manitoba Department of Natural Resources and the University of Manitoba. Considerable funding has been obtained through donations by the general public (with much assistance from a tame Great Gray Owl). Persons wishing to contribute to this project should send a check or money order to: Great Gray Owl Research Fund, c/o Robert W. Nero, Wildlife Branch, Box 14, 1495 St. James Street, Winnipeg, Manitoba R3H OW9. For further information on Great Gray's, see Nero's book, The Great Gray Owl, Phantom of the Northern Forest, c. 1980, now available in reprinted form through the Smithsonian Institution Press.
|Even larger numbers of Great Grays were involved in the winter movement of 1983-84 in which 407 owls were tallied in southern Ontario alone. Many owls ended up in suburban areas, where they sometimes had difficulty finding prey. That season in the Ottawa area, for example, pet shops sold a lot of mice to birders and photographers who fed them to hungry owls. Some birds were so used to being fed that when a car pulled up, the owls would approach it and wait expectantly. In some instances owls even learned to pluck mice from the hands of excited owl-feeders.|
A large concentration of Great Grays southeast of Winnipeg in late winter 1980-81 didn't fare as well. Copland and I recovered the remains of 50 dead Great Grays in two and a half months along a 35-mile stretch of the Trans-Canada Highway southeast of Winnipeg. No doubt there were others that died. Some, for example, were picked up by the Manitoba Highways staff before we contacted them. And injured birds could have made their way into adjacent woods before succumbing. Predators, such as fox and coyote, probably made off with still others.
Common Ravens fed voraciously on dead owls, occasionally eating most of the flesh and internal organs in a matter of minutes. Sometimes Ravens carried the remains of owls some distance from the highway. It became a race between us and the Ravens to retrieve birds. Whenever possible we made the rounds of the highway early in the morning, searching for live birds to band and looking for the remains of casualties. In three instances birds were found dead less than an hour after we had made a circuit of the zone of concentration. We suspected that most owls were killed by vehicles in the early morning, late evening, or at night, but several were killed during daylight hours.
Great Gray Owls evidently were concentrated along this busy divided highway because of an abundance of meadow voles in the extensive and heavily vegetated highway right-of-way. Extending back from the highway for as much as 100 yards, these broad stretches of grass and alfalfa provide excellent cover for voles. (The wide rights-of-way also help to keep white-tailed deer off the highway). The highway runs through known Great Gray breeding habitat, and the adjacent forest edges provide good perches for hunting owls. Of the 50 dead owls recovered in that period, 44, or 88 percent, were young from the previous summer, as were 20 of 24 birds captured and banded by us in the same area. Therefore, lack of experience with fast-moving vehicles may have been a mortality factor. Clearly one of the prices we pay for this excellent stretch of highway is an unavoidable loss of Great Gray Owls, at least in those years when large numbers of hungry owls are attracted to high vole populations alongside the highway. Nothing like this phenomenon has happened since then, despite good nesting in the area in summers 1984 and 1987.
Concerned about threats to Great Gray Owl breeding habitat in Manitoba and Minnesota from agriculture, energy, and forestry developments, Loch and I undertook a joint radio-telemetry study beginning in 1984 to determine lifetime and seasonal habitat requirements for the species in this region. Loch's work in Minnesota through St. Cloud State University already had shown that following a crash in vole populations, owls tended to move northward into Ontario. One of his females even stayed there and nested the following year. Accordingly, I set out to raise funds for the project under the auspices of the Manitoba Department of Natural Resources and the University of Manitoba. Fortunately, that first year we found 19 active nests and were able to radio-mark eight mated pairs and 11 of their progeny. Nearly all were at man-made nests. Sixteen of these birds were monitored for two months that summer by graduate student Maria Servos who obtained useful information on summer habitat use and prey populations.
The following winter there was a vole crash, and a majority of our owls moved out of the region, heading north and northeast. It required a great effort to keep track of the many radio-marked owls, but month after month Loch checked the birds from the ground, from the top of fire-towers (with increased height, signals can be picked up at greater distances), and from aircraft.
We learned quite a bit about the surprising mobility of the Great Gray Owl. Three months after one adult female disappeared from southeastern Manitoba her signal was picked up by Loch from an aircraft over the Hudson Bay Lowlands of northwestern Ontario! This was about 500 miles north from where she had nested. Unfortunately, logistical problems made it impossible to follow this bird any farther. By comparison, as shown by telemetry studies, Great Grays in mountainous areas of Oregon and California are almost sedentary. In general, those birds that moved northward out of southeastern Manitoba and adjacent Minnesota had better survival than those that remained. Several of the latter birds starved; 13 others, including five adults, were preyed upon by Great Horned Owls. We had previously recorded predation on Great Grays by these fierce birds. The results showed that, at least in a year when there was a scarcity of snowshoe hares and Ruffed Grouse, they could take a heavy toll of Great Grays. In any event, the forested peatlands of Manitoba and Minnesota clearly provide important nesting habitat for Great Grays coming from a large region of northern Manitoba and western Ontario.
Jim Duncan, a graduate student who has served as our project leader since the fall of 1985, now has evidence that nest-site selection may occur during the fall. How else to explain an adult female sitting in a nest in November? And, in the same month, two days or less after a nest was installed, it was visited by a Great Gray Owl. A radio-marked pair that raised a family in 1986 stayed together all winter and then successfully nested again the following year in the same nest. Surprisingly, there have been several observations of what ornithologists have called "helpers-at-the-nest." In one case, a non-breeding male twice brought food to a nesting female, even though her mate was bringing her all the food she needed. Hungry fledglings at times approached strange males that carried prey, and were sometimes fed. This fits in with similar observations in Finland and Oregon. U.S. Forest Service biologists Evelyn L. Bull and Mark G. Henjum recently reported that the Great Gray Owls' habit of nesting close together increases the likelihood of offspring survival. They suggested that in this respect Great Gray Owls "are unique in their sociability among North American owls."
When the male of a pair that was rearing one young was killed in a vehicle collision on a nearby highway, Duncan and several volunteers daily fed dead voles to the female parent, offering them to her on the end of a long pole. This was kept up until the young fledged, after which it was occasionally fed directly in the same way. I like the story Duncan tells of a close contact with another fledgling owl. In order to elicit begging calls from a brood of fledglings he was trying to locate, he imitated the call of a female parent. All three young suddenly came flying toward him in response to his calls. One of them, much to his surprise, landed on top of his head and remained there for a timed eight minutes; now and then it bent down and peered under his cap as if seeking to be fed.
Following a banner nesting season in 1987, when we found 26 occupied nests, 36 new owls were radio-marked. This includes eight adult males, 17 adult females, and 11 young. Transmitters on these birds are expected to last until early summer 1989. This should give us the time and opportunity to evaluate the productivity and survival of owls that emigrate northward. It was anticipated that before this past winter ended there would be a critical decrease in rodent populations. This should cause a majority of owls to move out of the tamarack lowlands (or peatlands) of southeastern Manitoba and adjacent Minnesota and into the northern part of the range. If birds that relocate in the north do not reproduce before returning south, the importance of southern peatlands for the maintenance of Great Gray Owls increases significantly. Should this prove to be the case, then more protection and greater care in the management of this diminishing habitat will be required in the immediate future. At this time there remains contiguous north-south tracts of forested peatland through which owls travel during their movements into and out of this region. Delineated to the east by the rugged Canadian Shield landscape and to the west and south by extensive agricultural lands, it would appear to be essential that at least some continuous north-south travel routes remain unbroken.
It is reassuring to note that the Roseau Bog, in which we really began our studies following the discovery of a Great Gray Owl nest there in 1970, and which we have continued to use as a study area, is now coming under management by the Minnesota Department of Natural Resources. A management plan for the Roseau Bog Owl Management Unit was completed in June 1987 by nongame specialist Katherine V. Haws of Bemidji. The plan addresses needs of the Great Gray Owl (and other species) on the 14 square-mile unit, and makes recommendations to harvest timber without adversely affecting owl populations in the area.
Despite the widespread protection of owls, their existence is still threatened. The factors of major concern are illegal shooting, accidental trapping in poorly-covered traps set for furbearers, pesticide poisoning, and especially direct loss or alteration of habitat.
Though the Great Gray Owl is but one of many owl species, its approachability and impressive stature allow us a close association with and increased appreciation for an ever-fleeting wildness.
Robert Nero is a Wildlife Specialist with the Manitoba Department of Natural Resources. He has authored two books, The Great Gray Owl: Phantom of the Northern Forest, and Redwings, both published by the Smithsonian Institution Press.||