When the nation's most treasured fliers have faced extinction over the past half-century — bald eagles, California condors and the majestic whooping crane — scientists have studied how to save them from deep within thousands of acres of forests and wetlands along the Patuxent River.
The crane has defined that work ever since a one-winged bird known as Canus, at the time one of fewer than 50 whooping cranes alive, helped establish the Patuxent Wildlife Research Center in 1966.
For decades, biologists at the center near Laurel overcame whoopers' scarcity by dressing as cranes themselves, wearing costumes while rearing the birds. Through trial and error, they learned ways around cranes' finicky reproductive capabilities, developing artificial insemination techniques and strategically stealing their eggs, a practice that coaxes them to lay even more.
But the era of the whooping crane — and perhaps of any captive breeding of imperiled birds — is ending in Maryland.
Nearly half of the Patuxent whooping crane flock is scheduled to be shipped off to Louisiana next week, and 200 acres of whooping crane pens are expected to empty by the end of the year. The Trump administration moved last year to eliminate the $1.5 million-a-year breeding program, run by the U.S. Geological Survey on a federal Fish and Wildlife Service refuge. Zoos and other private wildlife centers are taking over the work.
The decision is a pivotal moment at the research center, where generations of scientists have dedicated their careers to the whooping crane's survival. The center will remain open, but its focus will shift from breeding experiments to studies exploring the potential impacts of West Nile virus or offshore wind farms.
More importantly, some researchers fear it could mark a turning point in the troubled life of North America's tallest bird.
In some ways, the scientists' work is done — their mission is to study endangered birds, not farm them. And it has been a success. Since the early 1990s, they have raised enough chicks to maintain and grow four flocks in the wild, numbering close to 800 birds.
"We've been doing it for 50 years, but that itself isn't a reason to continue the program," said John French, director of the USGS Patuxent center.
The population growth masks the fact that the plight of the whooper is not solved, however. The species is far from self-sustaining because birds raised in captivity rarely succeed at rearing their own young in the wild. Scientists are still trying to figure out why, so captive breeding remains whooping cranes' only secure path to survival.
Some researchers worry the abrupt end to the Patuxent program could have lasting impacts on still perilously small whooping crane flocks. Even slight disruptions can prevent them from successfully breeding — new pens surrounded by chain-link proved that once in the 1980s — so the scientists expect it could take years before a new generation of cranes is born.
"It could end the Eastern migratory flock," said Joe Duff, co-founder of a recently abandoned 15-year effort to teach cranes to migrate using ultralight aircraft. That group of about 100 whooping cranes is one of only two migrating flocks, spending summers in Wisconsin and winters in Florida.
"They may not breed for another couple of years, if ever again," said Duff, CEO of Operation Migration. "Meanwhile, the Eastern migratory population was counting on those birds. The Louisiana flock was counting on those birds."
Whooping cranes numbered in the thousands across North America when the first European settlers arrived. But their size — up to 5 feet tall, with slender necks and long legs made for marshes — made them a popular target for hunters. The population fell to a few hundred by the end of the 1800s, and to a low of just 16 birds in 1942.
It's believed that only half of those whooping cranes were able to reproduce, and it took decades of painstaking work to bring any meaningful rebound.
It started with the arrival of Canus and a dozen eggs collected from crane summering grounds in Canada's Northwest Territories. It wasn't until the mid-1970s before any eggs were laid in captivity, and many never hatched. When they did, chicks often didn't survive.
Scientists routinely clip the wings of research subjects but quickly learned that practice prevented adult cranes from mating — the act involves the male flapping precariously onto the female — so they began keeping the birds in pens. They also developed artificial insemination processes, in collaboration with crane researchers in Wisconsin.
And they eventually realized they could rear even more cranes by donning white robes and head coverings, and delivering food through a long, lifelike beak of a crane puppet.
Soon, each season's brood grew from a handful of chicks to as many as 20 or 30. Scott Hereford, a biologist and manager of the Patuxent crane flock in the late 1980s, said there was a sense among the scientists that they were building momentum.
"It was a very exciting time," said Hereford, now a senior biologist at Mississippi Sandhill Crane National Wildlife Refuge. "We knew we were part of something really special."
By the early 1990s, the center had enough whoopers to split up the flock, creating new breeding programs managed by the International Crane Foundation in Wisconsin and at the Calgary Zoo in Canada. And the captive population finally started being released into the wild, building up new flocks, including the Wisconsin-to-Florida migrating flock and groups that stay year-round in Louisiana and Florida.
"It is the fruition of a tremendous dream," George Gee, a former director of the Patuxent crane program, told The Associated Press in 1993.
Those reintroduced populations now number more than 160, about the same number as are still being held in captivity, according to the crane foundation. The only fully wild flock, which migrates from the Gulf Coast of Texas to the Northwest Territories in Canada, has grown from its low of 16 birds to nearly 500.
"It's really miraculous," French said.
Yet the small flock nevertheless remains alarmingly vulnerable, he added. Whooping cranes have been a federally protected species since passage of the Endangered Species Act in 1973. Scientists estimate the population will have to grow to at least 1,000 — and maybe as large as 7,000 — to ensure its long-term survival.
A single storm or other weather disaster could significantly set back growth in the crane population, said David Curson, director of bird conservation at the National Audubon Society. And even under the best of circumstances, the birds' recovery will take decades because they don't reproduce until they're a few years old and lay relatively few eggs.
"It's a case of having all your eggs in one basket, literally," Curson said. "That's why it's really important to keep these recovery efforts up for the long haul."
The species' ongoing challenges led many crane scientists to use the same word in describing the end of the Patuxent crane program: "bittersweet."
"It's very sad to see it wrap up," said Glenn Olsen, a veterinarian who has worked with the Patuxent whoopers for three decades. He's not sure what's next for him at the center.
"In the current climate in Washington, a lot of our funding sources have dried up," meaning fewer opportunities to bring on graduate students or pursue field research, Olsen said.
Over the years Patuxent scientists have studied and bred captive bald eagles, masked bobwhite quail and Andean condors (a surrogate for their endangered Californian relative). In each case, as with the whooping cranes, the research has wrapped up as prospects for those species have improved, even if some challenges might remain for them.
French called the end of the crane program "a big moment, identity-wise" for the USGS research outfit. He said it's possible scientists could find another species at the brink of extinction to breed, but it's expensive, and attitudes toward the practice have changed — in part because of Patuxent's long history of trial and error with the whooping cranes.
Researchers found success dressing biologists in crane costumes so the birds wouldn't become desensitized to humans once released into the wild. But they fear those raised that way don't learn how to nurture and protect their young, leaving chicks prone to predators in the wild.
Similarly, a partnership of organizations dedicated to whooping cranes decided in 2015 to abandon a method of teaching chicks raised in captivity to migrate, leading them thousands of miles by ultralight aircraft. The practice was made famous in the 1996 movie "Fly Away Home," based on Operation Migration's work with Canada geese.
But the partnership decided it's best for cranes to start learning from their own.
Duff, Operation Migration's CEO, said he's concerned the changes in strategy could put progress in jeopardy. Operation Migration pulled out of the group, known as the Eastern Whooping Crane Eastern Partnership, earlier this year. U.S. Fish and Wildlife and USGS are founding members of the partnership.
"We don't believe it's being managed right," he said. "The closing of Patuxent is part of that."
While many researchers acknowledge the cranes' numbers could take a temporary hit as they adjust to new breeding grounds, some remain optimistic.
Wade Harrell, whooping crane recovery coordinator for U.S. Fish and Wildlife, notes that cranes can live more than 30 years — giving the flock time to adjust. One facility in Florida that has adopted some of the Patuxent flock is putting the birds in larger enclosures with more natural water sources and vegetation, perhaps better replicating what they would experience in the wild, he said.
"It's a bit of a hurdle to get through," Harrell said of the move. "I think long-term we'll be fine, and we'll be back to where we were."
Chesapeake Bay marshes were once within the population's winter range. But now, whether the loud whoops for which the crane is named are ever heard in Maryland again will likely depend on the success of breeding programs being scattered across the country — at zoos in Texas, Oklahoma, Nebraska and Canada, and at wildlife centers in Wisconsin, Louisiana and Florida.
The birds' voices come out in short bugle calls, squeaky and screechy like a noisemaker on New Year's Eve.
Hereford, the former flock manager now in Mississippi, said he'd never forget the chorus of cranes that grew louder with each year he was in Maryland.
"I can picture those grounds right now," he said. "It's really hard to imagine that being quiet."
Baltimore Sun librarian Paul McCardell contributed to this article.