People started gathering at the Lighthouse Missionary Baptist Church in southwestern Kentucky before sunrise. First there were just a few, sealed in their cars with the heat blasting, but before long there were close to 100, standing in the parking lot in multiple coats. It was the first Friday in December, 23 degrees at dawn and nearly windless. Everyone was looking up.

Operation Migration’s four ultralight planes floated into view over some oak and maple trees, then passed over the small, white chapel. An ultralight is powered by a massive rear propeller. In the sky, it looks like a scaled-down Formula 1 car dangling under the wing of a hang glider. Because the little planes taxi on three wheels, pilots call them trikes. At 200 feet, the first pilot, Chris Gullikson, was perfectly visible in his trike’s open cockpit. He was wearing his whooping-crane costume, a white hooded helmet and white gown that looked like a cross between a beekeeping suit and a Ku Klux Klan get-up. Gullikson and the other trike pilots were going to pick up the 14 juvenile whooping cranes that they were, little by little, leading south for the winter. Traditionally, and for many millenniums, cranes learned to migrate by following other cranes. But traditions have changed. Outside the church, a plucky, silver-haired woman named Liz Condie was explaining to the spectators why, exactly, her team has had to dress up and step in.

For the last eight years, Operation Migration has been one of several organizations collectively trying to bring whooping cranes back to the eastern part of the continent. The whooping crane is reclusive and headstrong — it demands a square mile around its nest to itself — and consequently was one of the first birds to suffer as humans crowded into North America. In a 1946 article in The New York Times, a spokesman for the U.S. Wildlife Service, which was then going through considerable trouble on the species’s behalf — much of it for naught — called the whooping crane “intolerant of civilization.” The article went on to blame the crane’s “lack of cooperation” for its looming extinction.

But the birds’ uncompromising wildness “is part of their majesty,” Joe Duff, Operation Migration’s co-founder and a trike pilot, told me not long ago. Thus, re-establishing the species presents a challenge: how can humans intervene to breed and teach the birds what they’ll need to survive without also wearing away those birds’ natural apprehension of people; without inadvertently building a race of whooping cranes that feels comfortable hanging out on golf courses and in schoolyards and the fetid little ponds around retirement communities? The birds would most likely find people in those places eager to feed them, and suddenly, you’d have whooping cranes that are hardly wild or majestic, but more like the irascible geese parked on the lawns of suburban courthouses — except that a goose, Duff told me, doesn’t jump into the air and rake forward with its long talons when it feels cornered. How, then, do you restore wildlife without simultaneously taming it? One way is to do it in disguise.

From the time Operation Migration’s cranes hatch at the federal government’s Patuxent Wildlife Research Center in Maryland, and for the rest of their lives, every effort is made to keep them from acclimating to humans or encountering even the slightest sign of them. Workers never speak around the cranes, and they always wear the same white costumes. They use a small crane-head puppet slipped over one hand to teach the chicks how to peck and forage. Gradually, the cranes “imprint” on the costume, accepting whoever is wearing it as the dominant bird in their cohort.

The chicks are then shipped to the Necedah National Wildlife Refuge in Wisconsin for “flight training.” Like many species, whooping cranes learn to migrate only by following their parents. They have no inborn understanding of where to go, and if no older birds are around to show them, they’ll just stay put. So the ultralight and its costumed pilot are introduced as a proxy. While still in their eggs, these cranes were played recordings of a trike engine, attuning them to it as a pseudo-parental presence. Now in Wisconsin, they spend their first summer learning to run, then fly, behind the aircraft. By fall, the whole entourage sets off for Florida, and Operation Migration takes its stage-managed show on the road.

The journey from Wisconsin to Florida is 1,285 miles long. Wild cranes can do it in as little as a week, swirling up to 8,000 or 10,000 feet on columns of rising air and coasting for miles. But the human-led migration takes longer — last year, it took more than three months. Trikes can’t keep up with the birds at such high altitudes, so they stay closer to the ground and force the birds to flap the whole way. And both the trikes and the cranes have fussy, sometimes opposing, requirements about what times of day and kinds of weather they’ll fly in. This year, Operation Migration left Wisconsin on Oct. 17. It was now Dec. 5, and they’d only managed to fly on 10 of the 49 days in between. They’d been grounded at this stopover in Kentucky for six days, by headwinds of up to 40 miles per hour, and they were still shy of the route’s halfway point.

2.

A voice broke in on Condie’s radio, and she narrated for the crowd outside the church. “O.K., they’re off and in the air, folks. We had one reluctant bird. No. 827 was the last one out of the pen.”

“He wanted to stay at my house!” a woman in the parking lot cried. Her name was Martha, and she owned the soybean field where the cranes had been hidden all week. Last spring, two team members showed up at her door with a satellite photo of her land, asking her to volunteer it as a stopover point.

Operation Migration relies exclusively on such hospitality. The organization, a nonprofit on an unforgiving $700,000 budget, gets almost no government money and so is left to scrape up the majority of its financing from individual donors. A cult of these so-called Craniacs now reads the crew’s daily journal religiously at OperationMigration.org, following the team and its numbered cranes like the cast of a reality show. (After Condie’s announcement, one woman explained to me that 827 is known for being “very independent.”) Along the route, well-wishers also bring the crew comfort food: very heavy hams, pots of chili. Already that morning, Condie was handed three batches of homemade fudge, several dozen donuts and a carrot cake. “Everybody puts on 10 pounds on migration,” she said later with a laugh. No one ever thinks to bring them a big salad.

The early-morning flyovers are the only opportunity for the Craniacs to even see the birds. The cranes must be moved from the refuge in Wisconsin to two refuges in Florida as furtively as fine art is moved between museums. From the time they land at each stopover to the time they can take off again, the cranes are stashed in a camouflage pen, tucked out of view and ringed by two electric fences. Costumed workers feed them twice a day, but otherwise the area is off-limits and resolutely guarded from trespassers, hunters, journalists and dogs. Martha (Operation Migration asked that I not disclose her full name) was sworn to secrecy, but it didn’t take. “This has been wonderful,” she loudly told acquaintances outside the chapel. “The best week of my life.”

Condie kept fielding questions from the crowd. “You only have to show the birds the way once,” she explained. After following the trikes their first year, the cranes continue migrating back and forth on their own each spring and fall. That very morning, in fact, graduates of the team’s seven previous ultralight-led migrations — 73 cranes in all — were scattered up and down the eastern flyway, at various points on their passage to Florida. Also scattered up and down the flyway were biologists — lots of biologists — from Operation Migration’s many partner organizations, tracking the radio signals emitted from those birds’ leg bands. And now that Operation Migration’s current class of cranes were airborne, its crew would hit the road, too, chasing the migration to its next stop in two motor homes, two pickups towing campers, and two vans, one towing a 50-foot supply trailer with a spare aircraft. All told, seven state and federal agencies and two nonprofits with an annual collective budget of $1.7 million in public and private funds were hard at work, fulfilling humankind’s responsibility to a bird that we’ve defibrillated out of near-certain extinction and gotten breathing again, if not yet absolutely saved.

The whooping crane, David S. Wilcove, a Princeton ecologist, told me recently, “is just about the most charismatic endangered species in America.” By 1941, only 21 wild ones remained. Today there are 381, enough to make it one of the most uplifting success stories in a field where the bar is admittedly sinking rather low. By now, one biologist told me, “work on any endangered species is certainly a very severe, rear-guard effort.” Twelve percent of the world’s bird species are threatened with extinction, according to the International Union for Conservation of Nature — so are a fifth of all mammals, and almost a third of all amphibians. In other words, we’ve backed ourselves into a corner, and sustaining the world’s wildlife will require progressively more systemic interventions from here on out. “Many of those species, probably most of them,” Wilcove said, “are in a certain sense wards of the state. Now and for the foreseeable future, they will be dependent on humans for their survival.”

Operation Migration exemplifies the kind of ingenious, unwavering work that needs to be done — and that we’ll need to keep doing, maybe forever, even as the strenuous administrative challenge of micromanaging so much of the natural world begins to blur the line between conservation and domestication. Already, it has come to this on planet Earth: men dressed like birds, teaching birds to fly.

3.

The hum of the trike engines swelled into a buzz. Then the lead pilot, Chris Gullikson, reappeared in the sky, drawing a lopsided V of tremendous white shapes behind his wingtips. As the parade of birds and machines coasted over the chapel and the three large wooden crosses driven into the ground beside it, people raised their binoculars and cameras to their faces and tilted back their heads. “It looks like a revival from up here, Liz,” a voice quipped in Condie’s radio. It was Jack Wrighter, one of the retired commercial pilots who flies top cover for the migration in his Cessna 172.

“There’s not a biologist among us,” Joe Duff told me later. (There is, however, a metal sculptor, a former butterfly breeder and Gullikson, who splits the rest of his year between leading adventure tourists into tornadoes and designing English-style riding saddles.) Duff, who is now 59, was a photographer in Toronto when, in 1993, he helped another ultralight hobbyist and artist named William Lishman — the first person to fly with birds — lead 18 Canada geese on a migration from Ontario to Virginia. “The whole idea was to use this technique for endangered species,” Duff told me. Soon the two men started practicing by costume-rearing nonendangered sandhill cranes and then migrating with them.

The nonprofit International Crane Foundation had been costume-rearing sandhills experimentally at the Necedah refuge in Wisconsin since a biologist named Rob Horwich devised the process there in 1985 as a tool for eventually reintroducing endangered crane species. Horwich theorized that crane chicks are similar to human infants, clinging to a parental figure who tutors or reassures them at various periods in their development. “Because of those periods,” Horwich told me, “you can have a tremendous amount of control over the animal.”

In the 1980s, Horwich led his sandhills around Necedah on foot, always in costume. As they made their first attempts at flight, he ran ahead of them like a boy launching a kite. But a decade later, Lishman and Duff were flying their sandhills outside the bubble of a refuge, and this meant having to fight even harder to keep them away from anything or anyone uncranelike. “It just kept getting more complicated,” Duff told me. A hinge on the pen might break in some farmer’s field, but “you can’t fix it, can’t bring a drill out there,” without someone in costume first walking the cranes a half-mile away, out of earshot. After five years they had honed a strict and effective protocol, and in 1998, Duff presented their work to the International Whooping Crane Recovery Team, the partnership of Canadian and American biologists charged by the two governments with reviving the species. “We were basically trying to ask the federal government to give us one of their most endangered species so we can dress up in a costume and lead it halfway across the country,” Duff recalled. “With a puppet.”

The whooping crane is the largest North American bird. It stands five feet tall and has a stiletto beak and a raspy call that carries for two or more miles. It is not particularly nice. (Operation Migration’s intern last year was short and unassuming, and whenever she suited up and got in the pen, Duff says, “the birds used to whale on her.”) The bird nests in marshes and all but vanished as the wetlands running down the center of the continent were drained for agriculture in the 1800s. The crane’s size, elusiveness and abrasive voice also seem to have made it a particularly satisfying trophy for hunters. (Washington Post headline, 1904: “Two Nebraska Duck Hunters Kill the Last of the Pompous Bird.”) It was one of the original species listed under the Endangered Species Act in 1973, when only a single migratory population of about 50 birds remained. Since then, staunch protection of its breeding grounds on the border of Alberta and the Northwest Territories and its wintering grounds on the Gulf Coast of Texas have allowed that lone, wild population to rebound. It is now up to 265 birds, an extraordinary turnaround but still not enough to give solid odds for the species’ long-term survival. So for 30 years, biologists have been trying to bolster that population by setting up a second, separate one. Operation Migration and its partners, known as the Whooping Crane Eastern Partnership, are just the latest chapter in that effort.

Reintroducing endangered species is rarely easy. Wild whooping cranes have evolved over 60 million years. There is no blueprint for engineering one in captivity, no key that might elucidate which of its behaviors are hard-wired genetically and which ones it must be taught. In 1975, biologists tried, essentially, to outsource the job of teaching cranes to survive in the wild. They replaced the eggs under female sandhill cranes in Idaho with whooping-crane eggs, hoping the sandhills would foster those chicks through maturity. They didn’t anticipate that the whooping-crane chicks would grow up sexually attracted to the species of bird that raised them and not to other whooping cranes. This confusion led to few new whooping cranes, though the birds did manage to produce one aberrant “whoop-hill” hybrid.

The biologists next tried to build a nonmigratory population. Beginning in 1993, juveniles costume-reared in Maryland were released on protected land in central Florida. Very quickly, however, bobcats and alligators devoured a great percentage of them. Eventually, the scientists realized that the birds weren’t roosting in water at night the way wild cranes do — a habit that allows them to hear the splashes of approaching predators. Apparently, this was a learned behavior, too. So back in Maryland, the biologists built new pens with ponds in them and started leading the cranes inside at sundown, propping up a whooping crane mannequin in each pond as a role model.

This helped, but once released in Florida, hundreds of birds were still eaten or died after ingesting stray metal objects, and the ones that did survive failed to produce chicks. Necropsies found that 10 percent or more had deformed reproductive organs — no one is exactly sure why. Last fall, after 15 years, the recovery team decided to stop shipping whooping cranes to Florida, shifting those resources instead to the more promising ultralight-migration program. Besides, projections showed development shrinking the nonmigratory birds’ habitat in Florida radically in the next 50 years. “We just didn’t pick a good spot,” Tom Stehn, the U.S. Fish and Wildlife biologist who is a chairman of the joint American-Canadian recovery effort, told me. “The question is, Is there a good spot left in the United States?”

Compared with these past efforts, the Whooping Crane Eastern Partnership has been an almost unthinkable success. It has also proved to be an awareness-raising juggernaut, with a sexiness that’s hard to come by for conservationists; the ultralight-led migration is covered in hundreds of local media outlets along its route and is a huge hit in classrooms. There is a serious problem, however: The whooping-crane population that the partnership has toiled to build up in the eastern United States has shown virtually no ability to sustain itself so far. The birds are abandoning their nests on the Wisconsin refuge, leaving their eggs to be eaten. It’s not clear why, but it may be that an infestation of black flies is harassing the birds, and they’re just getting fed up and walking away.

Whooping cranes don’t typically reproduce until they are 5 years old. But after seven years of guided migrations, Operation Migration’s cranes have successfully fledged only one chick, and biologists are concerned. The population is growing every year, but only because humans are rearing more birds in captivity, teaching them to migrate and putting them out there. Duff is confident the problem can be solved, whatever’s causing it, and that someday — when new generations of birds start materializing in Wisconsin and are led south by their parents — Operation Migration’s work won’t be necessary anymore. “I do anticipate that it’s going to work eventually, otherwise I wouldn’t bother,” he said. “But I don’t think it’s going to be as easy as we thought when we started.”

4.

After flying over the church, Chris Gullikson climbed with the birds to 2,000 feet, where the air was frigid but calm. He managed to lead the migration past its next planned stopover to the following one, a gated wildlife sanctuary in Hardin County, Tenn. It was a gain of 120 miles. A costumed pilot walked the birds down to a creek, allowing the crew to drive in and set up the pen. (After touching down, the pilots communicate by text message, setting their phones to vibrate.) The crew set up its camp on the opposite end of the property, then took turns showering and doing laundry in the sanctuary’s guest home. The owners had set out stacks of Domino’s pizzas and some Miller Lite for dinner.

The next morning, Richard van Heuvelen took his turn as lead pilot. The whooping cranes were hidden in the crook of a grassy, bean-shaped field. It was surrounded by pines and looked like part of a golf course. As van Heuvelen descended and swept around the back of the pen, the mob of birds rushed to follow the sound of his engine, the way dogs race along a chain-link fence when a car passes. He landed 100 yards from the pen door. Then he revved his engine, blasted an MP3 of a whooping crane call from a bullhorn on his rear axle and took off.

The door opened, and the cranes swept out in a rowdy blur. They formed a perpendicular line behind him, rising neck and neck, then rapidly sorted themselves into a V, 11 on one side and 2 on the other. This, once again, left crane No. 827 still inside the pen. (“Performance anxiety” is how one of the ground crew later explained it.) A costumed operative was hunched nearby, ready to lurch out under a giant, crinkly green tarp and scare the bird into the air, should the pilots call for the Swamp Monster.

“It’s a little rough down here, and they can’t climb,” van Heuvelen said over the radio. As soon as he turned south, onto the migration’s route and into a 12-mile-per-hour headwind, the flock fell out of alignment and scattered behind him. The headwind was not awful but strong enough that even if the birds could be persuaded to fly into it, they might not have the stamina to reach the next stopover, 57 miles away.

By this time, 827 had been jolted into the air, but he was lingering over a remote stand of conifers. Duff’s trike swept in to pick up the bird, but he ended up having to speed up and bolt by 827 to shake off a stall.

“One’s breaking off to the right,” another pilot, Brooke Pennypacker, soon radioed. “Do you see that one, Joe?”

“I see it,” Duff said. He had 827 lodged behind his left wing now and rocketed in to pick off this second drifter.

Meanwhile, a quarter-mile to the west, a thousand feet up, van Heuvelen was engaged in something akin to crane herding. He kept swooping under, and virtually through, the ragged white cloud of birds, putting his wingtip right in front of the cranes and hoping, again and again, to emerge with a neater arrangement filed behind him. Sometimes it worked, but as soon as he turned into the wind, the cranes would reshuffle and flap away. After half an hour, he turned back to the pen. Having traded the headwind for a tailwind, the cranes immediately locked behind him in a tight diagonal. He landed in the field, and the birds gladly shuffled back into the pen. Then the pilots headed for the hangar. The airport manager had sent out to Hardee’s for a big breakfast of sausage-and-egg biscuits to console them.

5.

As hard as it is to create cranes that will survive in the wild, making sure there is suitable wilderness to put them in may be harder. Globally, loss of habitat is the grimmest threat to endangered species, and it is no longer enough to simply seal off the habitat that’s left. Those ecosystems also must be managed as assiduously as the animals themselves.

Having disrupted natural fire cycles, we’re forced to suppress fires in some areas and set them in others. We control predators, mop up pollution or clear out invasive species. We slip contraceptives to overpopulations of deer and the plague vaccine to ferrets; call in sharpshooters in helicopters to assassinate every last feral pig from certain islands; teach California condors not to perch on power lines; pick up migrating salamanders and carry them safely across a California road; and install feeders to satiate the Devil’s Hole pupfish, a species of small blue fish that lives exclusively in a particular pool of warm water in the Nevada desert. “If humans had the inclination to give up, this would be the one species given up on,” Kierán Suckling, executive director of the Center for Biological Diversity, says of the pupfish. “You could say it wouldn’t matter — it has very few ecological interactions with anything else in the world. But just the opposite has happened. I think we’ve got a very unshakable ethic to prevent extinction in this country.

“A term that has come into use in the last couple of years is ‘conservation-reliant species,’ ” Suckling went on. “These are species that we can reintroduce successfully, but they’ll forever require active management.” They will last, in other words, as long as we keep rigging the world around them in their favor.

The term was proposed in a 2005 paper by a United States Geological Survey wildlife biologist named J. Michael Scott and several colleagues, including David S. Wilcove of Princeton. By now, Scott told me, it’s clear that the notion that we can roll up our sleeves, neutralize the threats to a species and walk away “is a flawed assumption.” According to data from the Fish and Wildlife Service, only 16 of the roughly 1,350 species in the United States ever listed under the Endangered Species Act have been recovered fully enough to be delisted, but only 9 have been allowed to go extinct. We should accept that, in many cases, shepherding a species to the point in between — keeping it conservation-reliant — is the only reasonable vision of success. It’s a concession, Scott said, that “right now, nature is unable to stand on its own.”

It’s difficult to imagine what a world of conservation-reliant wildlife might look like, how far we’ll go to prop up species in landscapes that have become drastically different from the ones they evolved to thrive in. Scott mentioned the example of the Columbia River, where endangered salmon are carried around hydroelectric dams in barges and where sea lions trying to eat the fish have been hazed with rubber bullets. His point was that we’re managing to balance the salmon’s needs and ours — including our need to keep salmon living in the Columbia River and not have the undoing of that particular facet of creation on our conscience. Then again, Scott added, with enough creativity and hard work, “I could keep polar bears in San Diego if I really wanted to.”

Eighty percent of the species on the endangered list are conservation-reliant, and the list is growing. Moreover, a study by Wilcove estimated that the actual number of endangered species in the United States is, conservatively, between 14,000 and 35,000 — the vast majority haven’t been studied closely enough or generated enough concern to get on the list. As Scott told me, if we want to preserve even some of them, and most of those turn out to be conservation-reliant, we’re talking about having to manually override a huge amount of the machinery of the natural world. Scientists and grad students will have to fan out, tending our Devil’s Hole pupfish and their habitat over here, and our whooping cranes and their habitats over there — fastidiously gardening the wilderness. “We’re in this for the long haul,” he said. “It’s the full-employment act.”

6.

Even as the recovery team jump-starts a new population of whooping cranes in the East, threats are gathering around the longstanding population of wild birds. Water is being diverted from the river that feeds the birds’ wintering grounds in Texas toward the ballooning San Antonio area. This, scientists at Fish and Wildlife believe, has raised the salinity of the refuge’s wetlands, reducing the population of blue crabs, the cranes’ main food source. Meanwhile, ponds of toxic tailings from the tar-sands industry are multiplying near the northern end of the crane’s migratory corridor, in Canada. And 40,000 wind turbines are projected to rise up along the route. (Collisions with power lines are already the leading known killer of the cranes during migration.) Then there’s climate change, which, among other things, is projected to put much of the crane’s current protected habitat underwater.

As our own population and its influence continues to expand, less free space remains for other species. “The animals that survive and thrive are those that do well in and around a human-oriented landscape,” John French, a U.S.G.S. biologist who oversees the whooping-crane research in Maryland, told me. The truest triumphs of conservation may be the species that rebound so phenomenally that they spill out of the refuges and recovery zones we set up for them and become a nuisance to us on our own turf, like the gray wolf, or the wild turkey and the white-tailed deer — both of which, in the early 1900s, were assumed to be doomed in the Northeast.

By now, French told me, the scientists overseeing the whooping-crane recovery are having a “sometimes very heated debate about how wild we actually want these birds we release to be. Is that the best thing for them? In my opinion, it may not be.” In other words, maybe the “Truman Show” existence that has been concocted for them isn’t actually doing them any favors. Maybe the most useful skill we could teach whooping cranes is how to coexist with people — if that’s even possible.

Still, all of those involved with the recovery I spoke to were confident about their ability to get the species on solid footing in the near term. And yet they were also perfectly willing to look the more worrying, longer-term picture squarely in the face.

“There’s no hope for whooping cranes in the long term,” Joe Duff told me back at the wildlife sanctuary in Tennessee, after that morning’s false start. In fact, if he looked ahead 50 years, he didn’t see hope for very much wildlife at all — or, he added plaintively, for his daughter, who is now 9 years old. “I think the world is facing a major crisis, and nobody cares,” he said. “I mean, we’ve left a mess. It’s a mess, and I don’t know what to do. Do you?”

Wilcove calls the whooping-crane recovery team “miracle workers,” and the resurrection of the bird in North America, provisional as it still may be, is a heroic accomplishment — and heroic in the somewhat Sisyphean way that any conservation work may be, since it requires rallying the will to build something you also realize the future is likely to erase. “I feel like I’m doing something useful,” Duff said. “I’m doing something, and I don’t know if it’s going to work out or be worth anything, but at least we’re trying. We try, and we educate and maybe — I’m thinking pessimistically, but I’m trying to be positive,” he went on. “Maybe you preserve a little bit of wetlands for something — and not just whooping cranes.” Or, he added, “maybe whooping cranes will survive when we don’t.”

That night, a belt of trashy air moved in. Then came a long chain of storms. Operation Migration wound up stuck in Hardin County for five more days. (The migration didn’t finally wrap until Jan. 23, and the team arrived in Florida with its budget in the red; donations from Craniacs were drying up along with the rest of the economy.)

One afternoon at the sanctuary, a crew member named Beverly Paulan suited up to let the cranes out of their pen for some exercise. The birds rose over the grassy field, then turned south around a dogleg and disappeared behind the pines. After three, maybe four minutes, Paulan started to panic. What if the birds didn’t return? But part of her, she later said, also wanted them to just keep going, hoping that they’d somehow figured out how to make it to Florida on their own.

She stood in her whooping-crane costume, flapping its wide, white sleeves. Then the birds came back.