On October 17, three small planes called "ultra-lights" lifted off from a wildlife refuge in the Midwest U.S. state of Wisconsin. Behind them were eight whooping cranes. They are among North America's largest and most endangered bird species. The ultra-lights were leading the birds to their winter home in the state of Florida, a journey scientists hope more whooping cranes will make each year.
Birds that migrate - in North America, that means flying south to warmer grounds for the winter - seem to know how to make the trip without following airplanes. But, the whooping cranes from Wisconsin were born less than a year ago at a U.S. government wildlife research center in the Eastern state of Maryland. They were moved to a wildlife refuge in Wisconsin this past July. Jennifer Rabuck is a spokeswoman for the U.S. Fish and Wildlife Service, which is part of the Whooping Crane Eastern Partnership.
"Normally, in the wild, cranes would just follow their parents, but there are no parents," she explains. "So, we are acting as those people [parents], showing them how to get from Wisconsin all the way down to Florida. Hopefully, as they become adults and raise their own chicks, they will be able to teach them this route that we have taught them, and establish a brand new flock."
A whooping crane is a tall, wading bird. A full-grown adult can be more than 1.5 meters tall. In the mid-1800's, there were 1,400 whoopers, as they're called. Hunting and habitat destruction reduced the population to 15 cranes by 1940. Today, there are about 400. About a third live in zoos or breeding centers. Close to 200 belong to a flock that summers in Alberta, Canada, and winters in Texas. A much smaller flock lives year round in Florida. Eastern Partnership biotechnician Dan Sprague says the crane chicks flown this year to Wisconsin are the start of a new flock. "We want each of these populations to be geographically isolated, so that, if a natural disaster or disease or something ran through one flock in one area, the others would safeguard the existence of the species," says Mr. Sprague.
Training for this trip began before the chicks were born. Sounds of humming ultra-light engines and the calls of adult cranes were played near the eggs in the days just before the birds were hatched. Dan Sprague says the goal of scientists is for the whooper chicks to reach adulthood, without having seen or heard a human. "When crane chicks hatch, they are completely helpless," he explains. "We use a puppet and a vocalization that an adult would use to communicate with them. We have to teach them to eat and to drink with this puppet."
The puppet looks like the head of an adult whooping crane. Its mouth opens and closes and is used to give food to the chicks. Any researcher working close to the cranes has to wear a special suit. It is a big, white, floppy, hooded outfit that makes the wearer look like a cross between an adult crane and a ghost.
Pilot Deke Clark says once the whooping crane chicks were moved to Wisconsin, work began to familiarize the chicks with the ultra-light planes. That meant the pilots had to wear the crane suits as they enticed the birds to follow the planes on the ground, using a recorded adult crane call.
"They start to reach the point of what they know is the airplane and us in the costume and the combination. They stay with you much better, and they do not have this propensity for turning around and doing odd things," he says.
The trip to Florida has been a slow one, usually covering no more than 130 kilometers a day. That is because the cranes are being made to fly in a way that is not natural for them. Wildlife Service spokeswoman Jennifer Rabuck says during migration, cranes usually fly high, riding warm air currents called thermals, and making large circles as they search for more thermals. To make this trip with the planes, the pilots need the birds to fly straight, more like ducks.
"So, a kind of compromise we can do is, just as a boat on the water produces a wake, as the ultra-light flies through the air, it produces the same type of wake in the air current," Ms. Rabuck says. "The first few birds in line get the easiest ride. The further birds are toward the back, the more they have to work, the harder they have to flap."
Once the team reaches the Florida wildlife refuge that serves as their winter home, the cranes are left to fend for themselves. In the spring, they will fly on their own back to Wisconsin. Dan Sprague says, in July, a new group of chicks will join the adults.
"You get very attached to them," he says, " but you also have to think about the big picture, which is, we want these birds to be wild animals. I do not ever look at them like pets."
Researchers hope the cranes will soon begin breeding on their own, and that the Wisconsin flock will reach 125 birds within 20 years.