In a nondescript building on a decommissioned Army base in Colorado last week, a man with a face mask opened a cardboard box, removed a black plastic bag, snapped the seal and pulled out a bald eagle.

A black mist of eagle down filled the air, some of it settling on the man’s Tyvek lab coat.

“His tail is really nice,” declared Dennis Wiist, a U.S. Fish and Wildlife Service specialist. He held the bird in two gloved hands, briskly considering the huge dark wings folded across its trunk, the talons locked in a final clinch, the beak slightly ajar.

“And a really good head,” Wiist said as he laid the bird on the stainless steel table and began probing with practiced fingers. “That’s good; we are desperate for good heads.”

It was that unmistakable white head — spotted by a Metro Blue Line commuter during rush hour — that launched this bird on its strange journey from a train track in Alexandria to the U.S. Eagle Repository on the outskirts of Denver, the only legal supplier of bald eagle parts used in Native American religious ceremonies.

There are few animals in the United States more shielded by law than bald eagles, a revered national symbol but a species that was nearly wiped out four decades ago. At least two acts of Congress make it a potential crime to possess even a single unauthorized feather. Which leaves, effectively, one source for the bald and golden eagle parts that American Indians consider a sacred link between the human and spiritual realms: this room.

“This is definitely very, very important to Native people,” said Bernadette Atencio, supervisor of the repository, who stood between the lab bench and two walk-in freezers where racks of eagle bodies hung, waiting to be shipped. There are more than 6,000 licensed members of federally enrolled tribes on the waiting list; some have lingered almost five years.

“I had no idea it was so involved,” said Robin Johnson, 60, the bird-loving commuter who first sighted the female eagle in Northern Virginia. “I’m glad to think of her being used like that, rather than just dying out by the tracks. It’s very spiritual.”

An eagle in distress

The final chapter of the Alexandria eagle’s life began one evening last month on Johnson’s regular Blue Line run from her job at a downtown law firm to her home in Fairfax Station. Somewhere between the Van Dorn Street and Braddock Road stations, a dark blur caught her eye. A glimpse of white-feathered head confirmed it: a bald eagle, not eight feet from the train window, flapping against a fence.

“I thought it might have been eating something,” she said. “I was so excited. I told everybody at work, ‘Oh my gosh, I saw a bald eagle.’ ”

She was less excited the next day when the bird was still in the same spot. Healthy eagles don’t hang out by train tracks. She got in touch with the Raptor Conservancy of Virginia, a rescue group, and then she and her husband got in the car. Driving along back streets near the tracks, they finally found the eagle next to a high chain-link fence. Its left wing clearly was damaged.

A couple of days later, on Feb. 25, Metro officials had organized a rescue run. A six-car train left King Street Station that afternoon, empty except for the train operator, three transit police officers, an Alexandria animal control officer and three volunteers from the conservancy. They found the injured eagle in some brambles about 300 yards past the Van Dorn station.

Finding hurt and dead eagles in the Washington region has become increasingly common as the species’s population has continued to rebound nationwide. Bald eagles were removed from the federal endangered species list in 2007. Some Native American tribes are pushing for the right to kill eagles for religious ceremonies, rather than wait years for the repository to deliver them. This month, the Fish and Wildlife Service granted its first-ever permit for the Northern Arapaho tribe in Wyoming to kill two bald eagles for religious purposes — a decision that has been questioned by some conservation and animal rights groups but reflects the dramatic comeback of the eagles.

“They’re doing fantastic,” said Matt Whitbeck, a wildlife biologist at the Blackwater National Wildlife Refuge near Cambridge, on Maryland’s Eastern Shore. In a census in January, 168 bald eagles were counted in the refuge. That’s up from fewer than 25 birds in the 1980s.

But more living eagles mean more dead eagles, including birds hit by cars and planes and electrocuted on high-voltage lines. “We’re going to see more and more of this sort of thing as the birds try to coexist with humans in places where they didn’t used to be,” Whitbeck said.

Kent Knowles, the Virginia conservancy’s president, has already shipped five dead eagles to the Denver facility this year. Initially, he was hopeful that the Alexandria bird could be rehabilitated. But after the rescuers threw a net over it, took it back to the train and rushed it to the veterinarian, hope faded.

“As soon as I saw the X-ray, I knew what was going to happen,” Knowles said. Whatever had collided with the eagle — he suspects a train — had ripped its left wing off just below the joint, making a stable amputation impossible.

After notifying federal wildlife officials of the findings, the vet injected a lethal dose of pentobarbital.

Knowles put the body of the eight-pound bird in a black plastic bag, sealed it and put it in a freezer in his basement. A few days later, the Fish and Wildlife Service sent a cardboard box and a packing label for Denver.

“This is not one of our more fun jobs, I tell you,” Knowles said as he nestled the bag into the packing peanuts and placed a sheet of paper reading “EUTHANIZED” on the top. “We’re here to help these birds.”

Birds, and pieces of birds

A FedEx truck has to negotiate four miles of remote road to reach the Eagle Repository, housed in a vast and largely empty former Army chemical weapons facility. Inside, a lobby display is filled with stuffed polar bears, cobra-skin boots and other illegally trafficked wildlife contraband that has been confiscated by federal officers.

But in the lab, it’s all eagles. A stack of shipping cartons sat near Wiist’s table, which was covered with lopping shears, pliers and the other tools of dismembering large birds. The repository receives about a 2,400 eagles a year from refuges and rehab centers around the country.

Wiist processes 25 to 30 birds a day, spending 10 or 15 minutes on each. He doesn’t seek a cause of death, preserve or clean the bird in any way. He merely checks to see which parts are suitable for filling the requests of Native Americans, which range from loose feathers to whole birds.

Some eagles, which may have been lying dead in the wild for weeks, are too decayed to use. Others offer feathers, under plumes, maybe talons. If parts are missing or rotten, Wiist will borrow from other birds.

“I’m noted for being picky,” Wiist said, a spectacular view of the distant Rocky Mountains in the window behind him. “People have waited a long time for these birds, and it means a lot to them.”

He quickly fanned the right wing of the Alexandria eagle, counting 10 primary feathers, 14 secondary. The feathers were intact but worn, probably from its time flailing by the tracks.

“It was getting ready to molt,” he said beneath his mask as he flipped the bird over to look at its left side. “Ah, this wing is pretty much torn off.”

Because the bird was injected with a killing drug, the repository will not use the trunk. Some tribes may use the organs for medicine bags, Atencio said, and officials don’t want to risk contamination.

Wiist’s verdict: The Alexandria eagle will provide a right wing, tail feathers and its head. Each part may fill a specific order, or be used to make other birds whole.

He reached for the heavy shears.

Worth the wait

The repository makes twice-monthly shipments of eagle parts that the recipients use for powwows, naming ceremonies and funerals from Alaska to Florida.

“We don’t ask what they want to do with them,” Atencio said. “Some are pretty secretive. The most interesting ones are probably the ones we don’t know about. ”

Most go to members of tribes in the Plains states or the Pacific Northwest. But some come to the D.C. area.

Marian Hansson of Indian Head, near La Plata, received 112 eagle feathers from the repository in 2010. A member of the Kiowa Tribe, most of whose members live in Oklahoma, she wove them into the headdress she wore for a ceremony marking her son’s military service.

Honoring warriors is an ancient use of eagle feathers, Hansson said, recalling her grandparents’ stories of such ceremonies.

“They represented a warrior’s valor and served as a reward for his coming back alive,” said Hansson, who also has an eagle feather fan from her mother and a cluster of feathers from a medicine bundle passed down from her paternal grandmother.

Hansson had to wait four years for her feathers from the repository, but she said she never considered tapping the robust black market in eagle parts. A single feather can fetch $150, according to Fish and Wildlife Service officials. A whole bald eagle can go for up to $2,000; golden eagles, which are in higher demand, are even more expensive. (The tribes are not charged for what they receive from the federal repository.)

There also are Web sites offering “legal” eagle feathers, which are typically painted turkey plumes.

But for tradition-minded tribe members, there is no substitute for the real raptor. And if that requires waiting for an eagle to die somewhere like Alexandria and for the wheels of the federal government to slowly turn, well, they take the long view.

“The eagle is considered a messenger between human beings and our creator,” explained Dennis W. Zotigh, cultural specialist at the National Museum of the American Indian in the District. “It’s our most widespread object of ceremonial use, and has been since prehistory.”