The Swan that Would Not Fly
Slow to alter their migratory habits, trumpeters face a deadly dilemma in the Rockies
Ruth Shea warned years ago that trumpeter swans in the Rocky Mountains were sitting on a time bomb. "Something's going to happen," she remembers saying, "whether it's disease or a deadly freeze-up." The Idaho Department of Fish and Game biologist feared that some catastrophe would threaten the last wild trumpeters of the Rockies as they huddled for the winter in the area where three states meet just west of Yellowstone National Park.
She was right. Three winters ago, a devastating blizzard ripped through the Greater Yellowstone area. It was the worst storm in decades, ushering in record lows and 60-mph winds. Almost every molecule of open water in a crucial part of their habitat turned to ice, locking up the bird's supply of aquatic plants. "We anticipated problems," recalls Shea, "but nobody expected the worst case."
Then came last winter and another blow, which compounded the impact of the first. Even before an unusually harsh arctic storm pushed temperatures to nearly—60 degrees F, the food supply in the swans' most important wintering site had mysteriously taken an abrupt and dramatic plunge. Record numbers of trumpeters were on hand. Starvation seemed imminent.
That a major flock of swans faced the possibility of a massive die-off was tragedy enough. But it was a double tale of woe for Rocky Mountain trumpeters. Rescued from near-annihilation earlier this century, the birds had begun to flourish, an apparent restoration success. Threatened again with disaster, the trumpeters stood to lose decades of hard-won ground toward recovery.
A crucial part of the problem is the species' reluctance to alter its behavior to adapt to changing circumstances. Trumpeters are birds of strong traditions. Cygnets learn from their parents where to spend the winter, then pass this information along to their young. Once learned, that location seldom varies: A trumpeter is more likely to starve to death in a familiar place than break tradition and pioneer to new wintering grounds.
Making matters worse, hundreds of the swans that gather on rivers at the juncture of Idaho, Montana and Wyoming are year-round residents, descendants of a flock that never learned to migrate. This stay-at-home tendency, combined with the swans' increasing numbers and dwindling food supplies, makes them sitting ducks when winter's blizzards blow in.
Fortunately, researchers last year were ready for the worst. In the largest swan-transport operation ever, a team of biologists led by the U.S. Fish and Wildlife Service stepped in to "teach" the trumpeters to look elsewhere for food. Now, as another fall shifts into winter, the rescuers wait hopefully to see if the birds have learned their lesson.
The trumpeter is one of two swan species native to North America. Its look-alike cousin, the tundra swan, numbers about 200,000, nesting in the far north and wintering as far south as California and the Mid-Atlantic coastal states. North America also hosts a third species, the mute swan, which was imported from Europe at the turn of the century to adorn ponds. But because of the mute's growing population (now at more than 4,000, mostly in the East) and voracious appetite for aquatic plants, many people consider the orange-billed bird a nuisance.
The trumpeter, largest of all waterfowl, sports a wingspan of up to 8 feet and a body weight that can exceed 30 pounds. Besides size, subtle differences in looks and behavior distinguish it from the tundra swan. The trumpeter has a longer black bill and, sometimes, a red "lip" along the lower half of its bill. Its low, hornlike call is a throaty contrast to the tundra's higher-pitched who-who.
Even experts have trouble telling the two apart when the species intermingle. Little wonder, then, that hunters occasionally shoot trumpeters—which are protected from hunting under the Migratory Bird Treaty of 1918—when the birds tag along with tundras, which, except in some areas, are legal game.
Trumpeter swans once ranged across all of North America. The birds nested during the summer across Canada, Alaska and the northern United States. Then they flew south just before fall freeze-up to ice-free waters in the Greater Yellowstone area, the Mississippi Valley and estuaries of the Pacific, Atlantic and Gulf coasts, among other wintering sites.
Because trumpeters fly low and slowly, they made easy targets for hunters poised along migratory routes. Between 1823 and 1880, the Hudson's Bay Company sold more than 100,000 swan skins, favored for their softness. By the early 1900s, most trumpeters in Canada and the Lower 48 states had been converted into meat, powder puffs, down bedding and quill pens.
In 1912, ornithologists declared the trumpeter doomed to extinction. All that remained, or so it seemed, were 50 adult swans and a handful of cygnets feeding in remote waters of the Greater Yellowstone area. Another 77 adults and their broods were later discovered at the foot of the Canadian Rockies near Grande Prairie, Alberta. In winter, these Canadian birds flew down to join their kin in the United States. All other migratory groups were feared destroyed, along with the trumpeters' knowledge of migration routes to warmer, more hospitable wintering spots.
In 1935, the U.S. government established Red Rock Lakes National Wildlife Refuge to provide safe summer habitat and a winter sanctuary where swans could survive with a handout of grain. The vast refuge lies on the western edge of the Tri-State wintering area, which includes Harriman State Park along the Henry's Fork portion of Idaho's Snake River, as well as Yellowstone National Park and the Jackson Hole area in Wyoming. Over the years, the descendants of those last Rocky Mountain birds prospered and multiplied, blessed by waters kept open by geothermal springs and generous handouts of grain.
Then, in 1954, a researcher in Alaska made an astounding discovery. Flying over the Copper River Delta one day, he spied what looked to be a huge flock of tundra swans. On closer inspection, he noticed that mixed among the tundras were hundreds of trumpeter swans.
An aerial survey in 1968 counted about 2,800 trumpeters in Alaska. As of last year, that number had soared to more than 13,300. These birds, known as the Pacific Coast population, migrate as far south as Oregon to winter and make up the largest concentration of trumpeters anywhere. Biologists believe the Pacific Coast flocks are completely separate from those in the Rockies. A third group, introduced within the past 30 years into parts of the Midwest, now numbers in the hundreds.
Last fall, the Greater Yellowstone wintering grounds hosted more than 2,000 trumpeters. Of that number, about 600 were year-round residents. The others, like their forebears, had flown in from nesting sites in Canada.
These growing populations prompted scientists to declare the swan's comeback a success. That was before various forces conspired to leave key sections of Henry's Fork—the most important stretch of Yellowstone wintering ground—with only sparse and spindly vegetation. Now, the celebrated size of the trumpeter population was a liability. The problem: too many swans in too small an area.
How had boom come to near-bust so quickly? Part of the answer has to do with lost knowledge, migratory traditions that were broken as the great birds neared extinction. Another factor, ironically, was the species' robust physical makeup. When temperatures plunge, most smaller birds must either move on or die. However, the trumpeter's enormous body enables the creature to store more insulating fat and thus wait out most bad weather.
The winter of 1988-1989 offered a grim preview of what was to come for Greater Yellowstone's trumpeters. When the arctic front moved in, forcing temperatures to 40 degrees below zero, it didn't take long for Henry's Fork—already low because of drought—to freeze solid. Their food trapped in cold storage and their fat reserves depleted, about 100 trumpeters died from starvation and exposure.
The following year offered a mild respite, which might have even added to the problem. Unprecedented numbers of swans congregated in the area to feed on vegetation already stressed by years of drought. By the time the birds returned last autumn, their food supply had dropped to a quarter of its normal level. Consequently the swans, each of which can devour 20 pounds of plants in a day, could not find enough to eat. "Time is up," lamented Ruth Shea at the time. "The food is no longer there. We have lost the major winter range."
Anticipating a potentially high death rate if the trumpeters remained in the area, the U.S. Fish and Wildlife Service—along with Shea and members of a dozen government and private agencies—began an emergency trapping program to transport swans to food-rich, open waters in southern Idaho, Utah and Wyoming. "What we were doing," as Shea puts it, "was forcibly broadening their horizons."
By November, about 500 trumpeters (about a fourth of the Rocky Mountain population) had gathered at Henry's Fork, with more dropping in daily. Crews struggled night and day to transport as many as possible before arctic storms swept in. Working at night, they dazzled the swans with spotlights, temporarily blinding them. "Then they scooped them up with a big net just like you'd dip-net a fish," says Rod Parker of Idaho Fish and Game. "We had people fall into the river; their clothes froze as soon as they came out of the water." Fortunately, no one was hurt.
Weary rescuers trucked the caged swans as far as 300 miles south, mostly to plant-rich bends in the Snake River. "All we were asking these birds to do was move up and down the same river system," explains Shea. "We weren't asking them to go to some area in Arizona and find their way across a thousand miles of desert."
The plan also called for a crew of 30 or more to haze the remaining swans with snowmobiles, air boats and sundry loud machinery—anything that might prod the birds to leave on their own. But on the morning in late December when hazing was to begin, the winter's first, bone-numbing "Siberian Express," as some weather forecasters called it, blasted the West. Oil seals blew. Fuel lines froze. "The first person went out and, about a half-hour later, came back with frostbite," recalls Shea. Hazing was called off.
In all, rescuers trapped and marked more than 350 swans at Henry's Fork and Red Rock Lakes and transported them to sites downriver. An undetermined number of birds were chased away by the commotion. Meanwhile, refuge personnel stood by at Red Rock Lakes to feed grain to any trumpeters that remained.
As many as 25 swans died in the storm. "But I'm convinced that, if we hadn't done anything, we would have had a much larger pile of dead swans," says Shea, who along with other biologists is now watching the area closely as cold weather approaches. "My best hope is that some swans will remember the new wintering sites and move to those places when conditions get bad."
If even a few of the relocated birds fly directly to their new wintering grounds this season, the rescue operation will be viewed as a success. "Chances are, a good percentage will show up right back in Harriman Park and we'll have to do the whole thing over again," says Rod Parker. "But," he adds, "we think that gradually we'll start to build up some knowledge of new areas in these birds, particularly the young ones."
While most efforts to restore swan populations around the country have failed, biologists in Minnesota have had remarkable success in getting their trumpeters to travel. "Our swans are migrating," says Carrol Henderson, who heads up the project for the state Department of Natural Resources. "They've been seen in Iowa, Missouri, South Dakota, Nebraska, Oklahoma, Kansas—the whole region south of us."
When Henderson started the program in 1979, he wanted to use trumpeter eggs from Red Rock as breeding stock. But at the time, as many as 90 percent of young Red Rock swans were dying mysteriously before they reached fledging age, so officials were reluctant to release any eggs. Undaunted, Henderson and crew started from scratch with an untested strategy.
Using pontoon planes, they gathered eggs from trumpeter nests in Alaska, then flew the fragile cargo to Minnesota for incubation. They raised the cygnets in captivity for two years. To prevent inbreeding, they brought in trumpeters from captive Canadian stock. "Just as the hormones started flowing," as Henderson phrases it, researchers paired and released the swans in northwest Minnesota marshes.
"For each four birds we turn loose, one of them is surviving to successfully breed in the wild," Henderson says, explaining that it takes two years for the swans to reach breeding age. Of the 149 trumpeters released to date, 10 pairs are now breeding and migrating the old-fashioned way. At that rate, the Minnesota project should achieve its goal of restoring 15 natural, free-flying breeding pairs two to three years ahead of schedule.
Why do the Minnesota swans fly south when those near Yellowstone won't do so to save their lives? Henderson attributes it to the "fly or die" technique. His project releases birds that have no parents to teach them bad migration habits. "Even though we raise them in captivity, instincts seem to take over," he says. The birds fly only far enough to reach food and open water—which may be only a county or two. But, unless they're sick, they invariably move south.
Ruth Shea believes dramatic measures akin to Henderson's fly-or-die approach are necessary to maintain the Rocky Mountain population. One important step, she says, would be to phase out the grain supply at Red Rock Lakes. Although grain sustains the refuge's flock, handouts work against efforts to disperse the birds.
Another step should be for wildlife managers to ensure adequate water flows in the area, she says. "We also need to figure out a way to scare most of the waterfowl out of the area and allow the vegetation to recover." One suggestion: "Every night, have a couple of technicians with bright lights go down the river making noise."
Inevitably, some swans will die as they are weaned from the Yellowstone area. Better, however, to lose a few than jeopardize the entire flock, say the scientists. "We need to take some big risks with these birds," Shea insists, "because their future is grim if they stay."
Judy Mills lives in Montana and writes frequently about wildlife conservation.