On a windswept fork of the Snake River, long-necked trumpeter swans glisten as white as the deep snow that frames the scene.
"Cross-country skiers love taking the trails along the river, because the swans alert to them but don't take off," said Keith Hobbs, who manages Harriman State Park. When the world's largest waterfowl do take flight, their 7-foot wingspans gently whoosh across the tops of the lodgepole pines.
Behind this serenity grows a mystery confounding wildlife officials and swan experts: Why hasn't the number of local swans increased over the years, even as their Canadian cousins are swelling in numbers? Some blame the Canadian trumpeters, which winter here and deplete food stocks that nourish those who live year-round in the tri-state region of Idaho, Wyoming and Montana.
But other swan experts say that even more than improved habitat, trumpeters need protection from hunters, who are confusing the majestic trumpeter with the more common tundra swan.
The U.S. Fish and Wildlife Service will announce this week whether it will consider listing the birds as threatened under the Endangered Species Act, something it has resisted.
The swans that reside here and nearby, in and around Yellowstone National Park, are the only trumpeters in the Lower 48 states to have survived near extinction in the United States in the 1930s. They were widely hunted during the previous 100 years for meat and quills for writing, feathers for fine hats and boas, and down for pillows.
The Canadian trumpeter, which also faced extinction in the '30s, has flourished from conservation efforts since then. But for the birds in this tri-state region, survival has remained a constant struggle. Efforts to relocate some of the swans to wilderness areas from Oregon to Nebraska have met mixed results, and the core flock dipped last year to 326, about 50% fewer than in 1988.
A pair of wildlife advocacy groups -- the Fund for Animals and the Biodiversity Legal Foundation -- has sued to compel the Fish and Wildlife Service to list the trumpeter swan as a threatened species. Among the issues being debated by federal wildlife officials is whether the local birds should be considered simply a flock of the thriving Canadian population or viewed as a geographically separate and distinct population in need of greater stewardship. Authorities aren't sure why local trumpeters haven't done better for themselves on the Yellowstone Plateau.
"These are spectacular birds and you'd assume there would have been a tremendous amount of research done on them," said John Cornely, the regional migratory bird coordinator for the Fish and Wildlife Service. "But the truth is, since they reside in such remote areas, there hasn't been much research.
"When there's a drop in the group's numbers, we're all concerned," he said. "But it comes down to a difference of opinion as to the cause. Maybe they've redistributed themselves due to the drought. What we do know is, we haven't come across a pile of dead swans."
But environmentalists suspect the flock is falling victim to swan hunting in Utah, where some tri-state trumpeters migrate in winter. Around Utah's Great Salt Lake, up to 2,000 permits are issued annually to hunters of the abundant tundra swan, which look similar to, but are slightly smaller than, trumpeters. Because of the similarities between the two birds, hunters are not held liable for mistakenly shooting trumpeter swans and are allowed to keep them after showing them to federal game officials for recording purposes.
Tom Aldrich, Utah's waterfowl program coordinator, said that last year, two trumpeter swans were reported killed and none were reported the previous year. He acknowledged that the accuracy of those counts rests on hunters' honesty.
"A very, very small harvest of trumpeter swans shouldn't have any overall effect on them," Aldrich said.
As a precaution, Utah closes the tundra swan hunting season if the deaths of 10 trumpeter swans are reported, but swan champions contend that far more trumpeters are killed by sport hunters of trophy birds who don't report to authorities.
"Swans have held a special place in society throughout history," said Ruth Shea, executive director of the Trumpeter Swan Society. "They have a role in art, literature, song, dance and in some religions.
"We came close to losing all the swans in this country in the last century," she said. "This was the only group that was not lost, but we haven't finished the job. It is especially appalling that hunters are allowed to shoot them with no liability."
Another wildlife advocacy group, Public Employees for Environmental Responsibility, complained in a report that the Fish and Wildlife Service "appears determined to keep a hunting season for swans open at all costs, even the potential loss of the tri-state [swan] population."
Andrea Lococo, a regional coordinator for the Fund for Animals, said "the government is playing Russian roulette with our last remaining trumpeter swans, simply to placate sport hunters."
Swan advocates believe that the tri-state trumpeters might have established a tradition of migrating to the Great Salt Lake by now, were it not for tundra swan hunters. But instead, they theorize, the trumpeters that are killed in Utah's Bear River Migratory Bird Refuge deprive the tri-state flock of its migratory-behaving pioneers, leaving them instead to compete for winter food with the Canadian flocks that fly here.
Federal wildlife officials haven't listed tri-state trumpeters as threatened partly because the number of birds fluctuates with no sustained downward trend. "We don't tend to put a lot of faith in any one year's numbers," Cornely said. "These are surveys done by biologists flying 100 to 500 feet off the ground in Cessnas, because these birds tend to stay in pretty remote areas."
Besides, he said, the decision hasn't yet been made whether to consider the tri-state trumpeters as a population separate from the Canadian birds. "We're trying to determine from a biological and evolutionary sense whether these birds are different and significant, and what their role is in perpetuating the trumpeter swan in North America," he said.
But Shea, who earned her master's degree in wildlife biology by studying the trumpeters around Yellowstone, said the tri-state swans should be treated just like bald eagles, which were given protection in the contiguous 48 states while they flourished elsewhere in North America.
"Just because there are thousands of trumpeters outside the United States," she said, "doesn't relieve our responsibility in protecting the ones here."