The Edmonton Journal
November 28, 1999.
BIRDS IN FREEFALL/ With their prairie habitat altered so radically, the future looks grim for the burrowing owl and possibly the barred owl
Owls, hawks in need of wise stewards
Journal Staff Writer
Moments before we ventured into the aspen woodlot just outside of Edmonton, Ray Cromie suggest on one say another word, lest we spook the barred owl we were seeking.
"If you hear a who cooks for you, who cooks for you all, that will be one of the owls," said Ben Olsen, a biologist studying the bird in Alberta. "Barred owl pairs usually make that call to establish territorial boundaries or warn each other of an intrusion by anything threatening a nest."
Cromie is a former Sherwood Park school principal who knows as much about owls in the Edmonton area as just about anyone. Somewhere in this woodlot is one of the 200 or so artificial nest boxes he has set up for barred and saw whet owls in the Edmonton area.
The barred owl is a rare sight in Alberta and could get rarer if stands of old growth forest continue to be cut down or fragmented. Like the more famous spotted owl which prompted forestry operations on the northwest coast of the United States to be halted, barred owls do not construct their own nests. Too big for the holes carved out by woodpeckers, they are almost entirely reliant on the hollowed out black popular typically found in old growth forests.
Cromies artificial nests are no doubt helping, as we were later to discover when we found a female barred owl nesting in one. But manmade nests are no guarantee that it and other boreal wildlife species will thrive in the future.
Scientist Joe Schmutz knows this all too well.
For 20 years he has been engaged in studies of the burrowing owl and ferruginous hawk in southeastern Alberta and southwestern Saskatchewan.
Thanks in part to the co-operation of local ranchers and farmers, he and several volunteers were able to put up hundreds of artificial nest boxes. He was hoping to reverse the slide in ferruginous hawk numbers caused by tree clearing and habitat changes.
But the ferruginous hawk, which is considered vulnerable in Canada, appears to be in decline again after a brief rebound in the late 1980s and early 90s.
The burrowing owl could disappear altogether in decades.
And the burrowing owl, which has been the subject of more than half a dozen studies and recovery projects, has been on a dizzy free fall that has not stopped. Since the 1970s, when there were more than 3,000 pairs nesting in Alberta, Saskatchewan, Manitoba and southern British Columbia, their numbers have plummeted at an annual rate of around 16 per cent. Today, the burrowing owl is no longer found in Manitoba. It nests in tiny numbers in B.C., thanks only to capture and release programs. And in the burrowing owl heartland of Saskatchewan and Alberta, there are now fewer than 1,000 pairs.
Canadian Wildlife Service scientist Geoff Holroyd warns the burrowing owl could disappear altogether from Canada in the next few decades if the declines continue.
Habitat fragmentation, pesticides, predators and limited food availability have all been implicated, but no one has been able to determine why the species is disappearing so quickly.
There has been no serious alteration of the owls habitat over the past 20 years, and co-operative farmers have refrained from spraying pesticides near owl nests.
Holroyd and Jason Duxbury have spent the last few years in Texas and Mexico trying to determine if something on the wintering grounds may be causing problem. But so far, theyve only been able to find two birds in Texas.
And time is running out.
Biologist Darcy Shyry recently conducted an intensive survey of burrowing owls in Southern Alberta and concluded they could disappear within 15 years.
Even if the scientists finally figure out where most of the burrowing owls are wintering and whats causing their declining numbers, Schmutz believes it may not matter in the long run.
"If you look at the bigger picture, its not just owls that are in trouble on the prairie grasslands," he says.
"Surveys over the past couple of decades have documented some pretty serious declines of spragues pipit, loggerhead shrike, killdeer, short eared owl and western meadowlark. Weve also seen reduced productivity of both Swainsons hawks and ferruginous hawks, and their main prey, the Richardsons ground squirrel. The prairie habitat has been so radically altered that those birds whose populations have dipped below critical thresholds, are not going to come back."
One has to go back to the days before the Prairies were settled to understand what has been happening, according to Schmutz.
With the arrival of Europeans, millions of bison and antelope disappeared. Their demise forced large carnivores such as the prairie grizzly and the wolf into the boreal forest and more remote mountainous zones.
The presence of so many people also put an end to prairie grassfires, irreversibly altering habitat conditions for those species that remained. Animals such as the coyote exploited the changes. Others did not. Even the grasshopper may have been affected. The last major outbreak of grasshoppers, a staple in the diet of the burrowing owl, occurred in 1986.
"What were seeing today on the Prairies is a continued response to changes in habitat that occurred a long time ago," says Schmutz.
"I suspect were going to continue to see more responses down the road. And if Im right, I expect well see the same happen in the boreal forest environments with all of the clearcutting and oil and gas development that is currently going on."
University of Alberta scientist Fiona Schmiegelow believes its too early to say whether the catastrophic changes that have occurred on the Prairies are also going to happen in the boreal forest.
But she says its folly to suggest we shouldnt worry because there has been no boreal species collapse since oil and gas activity began 50 years ago and since forestry developments were launched in earnest earlier this decade.
Whats happening to the warbler could happen to the barred owl
"In Finland, scientists are still seeing responses to habitat fragmentation from forestry developments that occurred earlier this century," Schmiegelow says. "When youre dealing with species with relatively long life cycles, its possible for a very fragmented habitat to sustain residual populations for some time."
Most of her work on habitat fragmentation in the boreal forests has been done on birds. In one ongoing experiment, she is looking at what happens to the black throated green warbler in an old growth forest environment with a single clearcut passing through.
Five times throughout the breeding season, she and her associates go to a series of stations and do a five minute count of all birds seen and heard.
"In the fragmented areas, weve seen about a 50 per cent decline of the population over the past five years," Schmiegelow says.
"Just how significant this is is unclear. What happened on the Prairies was a near complete land conversion. Whats happening in the boreal forest is much more subtle in terms of habitat loss and fragmentation."
Oslen suspects what is happening to the warbler could happen to barred owls and other bird species that rely on old growth environments.
Barred owls will readily occupy young forest stands when artificial nesting boxes are provided, he says.
But Olsen and other scientists dont believe that is the solution for the barred and other species because changes in habitat can also leave them more vulnerable to predators such as great horned owls that exploit new growth forests.
While no one can say for sure what is likely to happen to owls, hawks and other birds of the boreal forest because of resource development and urbanization, naturalist Terry Thormin thinks he may have had a glimpse into the future.
Twenty five years ago, he drove to Wagner Bog, a few kilometres northwest of Edmonton, with a parabolic reflector to see what the night would produce. In the five minutes it took to do the 360 degree scan, he recorded or saw 13 saw whet, eight boreal, two great horned and two long eared owls.
"It was an amazing night," recalls Thormin, one of a number of scientists, local residents and conservationists whove successfully lobbied to have Wagner declared a natural area.
"Of course, I couldnt do that again because they built Highway 16 through the spot I was standing on. But my gut feeling is, were never going to get another night like that out there. Theres just too much development thats gone on out there over the years for Wagner to sustain those kinds of numbers."