Nearly grazing the treetops, a tiny red plane swoops in dizzying circles over the bogs and forests of Canada's Wood Buffalo National Park. As pilot Jim Bredy banks hard for another pass, he and his two passengers press their faces against the glass, squinting to spot familiar white smudges on the ground—adult whooping cranes—with russet-feathered young in tow. This wilderness is the summer home of the last wild migratory flock of Earth's most endangered crane.
The aerial census takers are Bredy, Tom Stehn of the U.S. Fish and Wildlife Service, and Lea Craig-Moore of the Canadian Wildlife Service (CWS), and they're worried. The flock's population had reached 266 in the spring of 2008. But by the following spring, 57 had died, 23 of them on the birds' wintering grounds in south Texas, where drought had decimated their main food—blue crabs and a plant called wolfberry. Others probably perished during migration, often after striking power lines, the biggest known killer along the flyway. The higher-than-average death count has added urgency to a new effort that tracks some migrating birds with GPS anklets.
Still, whoopers, as they're called, aren't nearly as bad off as they once were. A key event in their revival took place 42 years ago, when CWS biologist Ernie Kuyt went on a spring treasure hunt. A helicopter let him off on the soggy boreal landscape, a vast expanse of sedge meadow and ponds broken up by islands of black spruce and willow. Using a jack pine pole as a staff, he trudged through muck that might have stolen his resolve—and his boots. At the heart of a shallow pool, he spied a massive nest cradling a pair of blotchy eggs, each the size of an Idaho potato. Kuyt had left his container in the copter, so he tucked a sole egg into a wool sock, sensitive to the weight of the future life—and the possible salvation of a species—he'd carry home.
Kuyt's excursion marked a major step in the now decades-long effort to save the whooping crane, begun by the National Audubon Society's Robert Porter Allen and others in the 1940s. The egg in Kuyt's sock helped seed the captive-breeding program that is crucial to the species' rescue. Multiple flocks once crisscrossed the continent, but numbers fell drastically in the mid-1800s as settlers converted wetlands to farms and shot birds for meat. When a major storm in 1940 led to the petering out of a flock in Louisiana, at most 22 wild whoopers remained.
The bird has become the emblematic endangered species, thanks in part to its fierce charisma. Standing nearly five feet tall, it can spy a wolf—or a biologist—lurking in the reeds. It dances with springing leaps and flaps of its mighty wings to win a mate. Beak to the sky, it fills the air with whooping cries. The sole wild flock, listed under the Endangered Species Preservation Act in 1967, has slowly expanded. At the same time, conservationists have hatched and bred the birds in captivity and reintroduced them to their former habitat, boosting the total—including captive stock—to more than 500.
To rescue this darling among the world's 15 crane species, scientists first needed to answer a burning question: Where did whoopers nest—and lay eggs—in summer? Since the late 1890s biologists had known that the wild flock wintered on coastal marshland in what would later become the Aransas National Wildlife Refuge in Texas. To crack the summer mystery, officials asked citizens to report sightings; volunteers combed the migration route for clues. Then, in the summer of 1954, a report came from a fire helicopter flying over a virtually inaccessible wetland some 2,500 miles north of Texas, on northern Canada's boreal plains. A whooper family was on the ground. By lucky chance, the flock had settled inside Wood Buffalo, the biggest national park in North America.
The remoteness of the 17,298-square-mile wilderness, set aside in 1922 for Canada's last wood bison, has aided the cranes. Here whoopers face only natural predators—wolves, bears, foxes, egg-stealing ravens—as they guard two-square-mile territories, nest hock-deep in water, and raise one or sometimes two chicks on a diet including insect larvae, seeds, snails, and fish. "Wood Buffalo is and always will be truly wild," says Tom Stehn. "The birds are safe here."
Back overhead, the red plane dips to the west as Craig-Moore excitedly calls out another sighting. Even with GPS coordinates from past surveys, it will take multiple flights over several months—59 hours in the air—to finish one season's count of 62 nests, 52 chicks, and 22 fledglings spread over 100 square miles.
As of February 2010, the cranes' annual tally sat at 263. So they are holding steady—but remain at great risk. In Texas, water diversion for farms and suburbs is boosting salinity in coastal salt marshes, killing the crabs that cranes eat in winter. That land is already vulnerable to storms and rising seas. Lost wetlands, oil sands development in Alberta, and wind power projects also mean fewer resting spots on the flyway. "The best wind flows along the migration route," says Stehn, "and there are plans to erect thousands of turbines." Windmills themselves may not present major obstacles, but power lines will. "It shows how fragile a success story this is."
Today's population must expand at least fivefold before bird advocates can truly rest. But veterans of the effort are optimistic about reaching that goal. Says CWS biologist Brian Johns, "With enough habitat protection, in a couple of decades maybe the population won't need us anymore. Maybe we can finally leave the cranes alone."
Come October, the cranes at Wood Buffalo prepare for an ancient ritual, the weeks-long journey to their Texas wintering grounds. Strutting across the spongy earth, an adult male tilts his head, one yellow eye peering skyward, waiting for his weather cue: The arrival of thermals that will carry his family aloft. As the air begins to shimmer, he leans his long body forward, signaling his intention. His mate and young quickly copy the posture. And then, in near-perfect unison, they take off.