Cranes and their planes: heading south
Any day now, 21 endangered whooping cranes will leave a Wisconsin marsh and head southeast to a Florida marsh, tracking close behind their "parent," a loud, slow-moving, winged beast better known as an ultralight airplane.
Another nine whoopers are expected to follow the 77 adult cranes that summered at Necedah National Wildlife Refuge in central Wisconsin.
The whooping crane was once the rarest of birds. It stands five feet tall, has a wingspan of seven feet or more, utters a peculiar trumpeting sound, and performs a captivating dance. The bird is white, except for a red head and black feathers at the wingtips.
At Necedah, both the 30 first-time migrants and the 77 adults are progeny of a tenacious campaign to return the bird from the edge of extinction. All of the approximately 544 whooping cranes alive today descended from 21 birds that had survived hunting and habitat destruction in 1941.
The effort to establish the Florida-Wisconsin flyway is managed by a collaboration of private and government agencies called the Whooping Crane Eastern Partnership.
Outside of pictures, few people get to see snow-white birds trailing gawky flying machines. Although this confluence of old and new arrests attention, the whooping crane deserves affection on its own terms, says Joe Duff, an ultralight pilot who has spent long hours in close proximity to this endangered species. "How can you not love them? They are hugely arrogant - 'I am here, whether you like it or not!' They make a call you can hear for four miles. They have been around for 60 million years, have seen the shift in continents, and then we came along and forced them close to extinction."
Duff is CEO of Operation Migration, the recovery partnership's air force.
Needed: New migratory flock
The need for another migratory flock is evident from a look at the crane's perilous history outside of captivity:
Half of a non-migratory flock was killed by a hurricane in Louisiana in 1940; the rest of the flock vanished by 1950.
A non-migratory flock of about 40 whoopers in Florida has stagnated, and is not receiving new captive-bred chicks.
A flock of about 247 birds (all descended from 15 wild whoopers alive in 1941), continues to migrate between Wood Buffalo National Park in northern Canada and Aransas National Wildlife Refuge in Texas. Last winter, drought reduced river flows at the refuge, and as the marshes grew saltier, the blue crab moved to deeper water, and about 20 whoopers died as it became more difficult to reach their primary food. The incident shows that further drying, due to weather, climate change or development around the marshes, could reverse years of stringent protection for the whoopers.
Any small population is also vulnerable to predators and disease, and a key survival tactic for whooper enthusiasts is to disperse the cranes into new flocks. But establishing a new migratory flock is no simple endeavor. Normally, cranes learn their migration route from other cranes, but how do you start a new route in the absence of an established flock?
A previous effort to have the whoopers follow sandhill cranes failed, and only one aircraft can fly slow enough to lead cranes: the ultralight. On a level flight, whoopers average 38 miles per hour, just above the ultralight's 32 mph minimum.
Since 2001, Operation Migration's ultralights have been leading cranes more than 1,200 miles from breeding marshes in Wisconsin to winter marshes at Kissimmee Prairie in Florida. Because cranes must flap their wings while following the ultralight, they can only fly an hour or two a day, so the southbound flight can take two or three months. Normally, whoopers loft on warm, rising air and then soar ahead. This energy-saving tactic allows them to cover several hundred miles in a day.
Eyes on the skies...
Eager to witness cranes tracking ultralights, The Why Files visited the Necedah, Wis., refuge during the annual meeting of the Society of Environmental Journalists, held in Madison. Just our luck, the winds grounded the ultralights, so we could not watch their crane-training flights...
Flying with the cranes looks like fun, but it's a "huge amount of work and a huge responsibility," says Duff, who co-founded Operation Migration in 1994. "These birds off your wing represent the work of many people, and you've got a responsibility to yourself to stay safe. You are checking the GPS, watching for obstacles, and you don't have time to look out and enjoy the flight."
Cranes are strong-willed and assertive, Duff adds, and may try to lead the ultralight rather than follow it, and the result is a "choreographed aerial rodeo" as pilots try to stay ahead of the cranes. "Sometimes a bird will find a thermal and not want to land, and have to be chased all day."
Three ultralights are available to guide stragglers, but occasionally a bird that insists on landing must be caught by ground trackers and trucked to the next night's crane-corral.
During eight trips south, and nearly 10,000 miles of crane commuting, the operation has not lost a pilot -- or a bird, says Duff.
In 2008, Operation Migration altered its southbound route to avoid "trashy air" over the mountains in Tennessee, Duff says, but building a new route is no simple matter. After identifying remote marshes on maps and photos, the group offers the owners an unusual sales proposition: "Hi, we're leading birds south. Can we take over your property and park our motor homes here? That wetland down below, you won't be able to go down there. And we don't know when we will leave."
Despite such a rigorous "ask," most landowners are "hugely supportive," says Duff. "They open their houses to us, often make dinner for all 12 of us, and then we may fly right past in good weather."
Cranes learn the migration route after a single trip south, Duff adds. Although they return fairly close to their southbound route, they revert to the normal soaring flight, which allows them to cover the migration much quicker than the energy-intensive flapping used to follow their ultralight momma.
"We leave them with nothing except the memory of the route," Duff says.
With 77 adult birds in the Wisconsin population, plus 30 that were added this spring, the Wisconsin-Florida flock seems close to its goal of 125 birds in a sustainable population, except for one bummer: the whoopers are abandoning their nests. "The birds on the reserve form pairs fine, build nests fine, lay eggs fine," says John French, research manager at Patuxent Wildlife Research Center in Maryland, a headquarters of whooping crane survival, "and they begin the incubation fine, but almost every nest is abandoned part way through. It's the biggest problem, and we don't know why."
2009 whooping crane populations
A key suspect is clouds of black flies, which elsewhere have forced common loons from their nests. If further studies convict the flies, the Necedah refuge may use targeted insecticide sprays, says manager Larry Wargowsky, or perhaps change how it manages water to reduce fly numbers.
Surviving the bottleneck
Nest abandonment could also signify a deeper difficulty, says French. The crane was "essentially extinct... and it's possible that they have a genetic inability to deal with stress; have very little ability to withstand chance events." A drastic population crunch has forced the cranes through a "genetic bottleneck" that stripped away the genetic diversity it could need to survive disease and other changes in the environment.
Still, the major story about whoopers is survival, not poor genes. "A lot of geneticists said the whooping cranes could not survive, but they did not tell the whooping cranes," says George Archibald, co-founder of the International Crane Foundation, another component of the whooper partnership. "Their rate of increase [in the wild] has been absolutely normal, but they do seem much more prone to accidents; they are very fragile."
Terry Devitt, editor; Steve Furay, project assistant; S.V. Medaris, designer/illustrator; David Tenenbaum, feature writer; Amy Toburen, content development executive