The exact techniques migrating birds use to find their way across thousands of miles to exactly the same spots year after year are only partially understood. Watching for landmarks is clearly part of it—but equally clearly, it’s not the whole story. Certain types of birds have been shown to rely only minimally on vision, in some cases apparently getting their bearings from the Earth’s magnetic field. Be that as it may, some bird species have strong migratory instincts, while others (including geese, ducks, and cranes) must be taught the way to and from their winter homes. A single demonstration is enough to program the route into a bird’s memory, but what happens when a bird never gets that first demonstration? It has no idea where to go, and as a result, its survival is threatened if it can’t find enough food when the seasons change.
This situation poses a unique problem for certain birds raised in captivity, such as the whooping crane (Grus americana)—the tallest flying bird in North America, with a height of up to 5 feet (about 1.5m) and a wingspan as wide as 8 feet (about 2.5m). By the middle of the 20th century, the worldwide population of wild whooping cranes had dipped to only 15, bringing the species perilously close to extinction. (A century earlier, there had been about 1,400 of them—and even that was a dangerously small number.) As a result of diligent conservation efforts, those few remaining birds were protected in the wild, and their numbers gradually began to increase; today, that flock numbers about 200. Meanwhile, some of their eggs were hatched in captivity to breed a “backup” flock, in case some natural disaster (such as a hurricane) wiped out the others. After several years of careful breeding and release, a non-migratory flock of nearly 100 is now living in Florida. However, what everyone wanted to see was the reestablishment of another migratory flock—a group of whooping cranes that spent their summers in Wisconsin and their winters in Florida, just as other flocks had done decades earlier. But although the birds could be bred and released successfully, there was no apparent way to teach them a safe way to fly from one home to the other.
William Lishman, a sculptor and filmmaker living in Ontario, wanted to be a military pilot but, being color-blind, couldn’t pass the required vision exam. So instead, he took up hang gliding, and soon moved on to fly one of the first ultralights—an aircraft that was basically a hang glider with a frame underneath that supported a small engine and propeller. After seeing a film in which geese followed a boat, Lishman wondered if they might also follow an ultralight. After three years of experiments, he finally managed to lead a small flock of Canada geese on a flight near his home in 1988. Within a couple of years, the scientists working with whooping cranes contacted Lishman and proposed that he use the same technique to teach the cranes how to migrate south for the winter.
The first step was to try teaching a flock of Canada geese (which are not endangered) how to migrate over a long distance; that way, if anything went wrong, at least the losses would be less severe. In 1993, Lishman and fellow ultralight pilot Joe Duff led 18 geese from Ontario to Virginia, 400 miles (about 650km) away. In 1994, those geese found their own way back to Lishman’s home in Ontario, proving that the system could work. That year, Lishman and Duff founded a nonprofit organization called Operation Migration to oversee and raise funds for the much more significant effort of teaching whooping cranes to migrate. (Meanwhile, Lishman assisted in the development and making of the 1996 film Fly Away Home, a fictional story based on his life and work.)
In 1997–1998, Operation Migration performed another migration experiment, this time with sandhill cranes (a non-endangered relative of the whooping crane). One of the things they learned in this process was that cranes imprint strongly on humans. The result was that the birds were more interested in finding and staying with people than in returning to their homes—not the result Operation Migration was looking for. So they refined their techniques to make the humans invisible to the birds; the process begins just after incubation.
Are You My Mother?
Even before the eggs hatch, the cranes hear recordings of an ultralight’s engine, so that they’ll become accustomed to and comfortable with that sound. When the chicks hatch, the first thing they see is a hand puppet that looks like a crane—so they imprint on that. All the humans who interact with them are dressed in baggy white costumes that thoroughly disguise their form; they also carry one of the puppets at all times and avoid talking. That way, the cranes may have the impression that their “parents” are rather funny-looking, but not that they’re human. Shortly thereafter—before they’re old enough to fly—the birds are trained to follow a rolling machine that looks (and sounds) like an ultralight. Eventually they begin following a real ultralight, and when it takes off, the birds follow it into the air. After several weeks of training, the birds are ready for their big trip.
The first attempt to teach whooping cranes to migrate took place in 2001. Three ultralights led a flock of eight birds over 1,200 miles (about 1,900km) from Wisconsin to Florida. One of the birds died after hitting a power line in a storm, but the other seven made it safely—and returned without any assistance the following spring. The effort has been expanded in the years since, and now more than 40 whooping cranes are migrating on their own in this new flock.
Although more chicks are bred and released using aircraft-assisted migration every year, the overall effort is a matter of “three steps forward, two steps back.” A number of the birds have been killed by predators; others die from illness or other injury. So although the flock continues to grow, the pace is slow. Still, Operation Migration (along with several partner organizations) continues to improve their techniques with the goal of enabling an ever greater number of whooping cranes to fend for themselves. In time, the whooping crane may make it off the Endangered Species List, and they’ll have an airplane to thank for it. —Joe Kissell