Scientists are anxiously watching the skies to see if the Chesapeake’s largest native waterfowl will return on its own this winter — two centuries after it was wiped out here.

Since 1997, biologists have been teaching migration routes to trumpeter swans by training them to fly behind an ultralight aircraft — a technique used successfully with Canada geese and sandhill cranes, and popularized in the movie, “Fly Away Home.”

After a successful experimental migration from Virginia to the Eastern shore in 1997, biologists last year tried to teach the birds to migrate from what is hoped will be their permanent summer home in Genessee County, NY, to wintering grounds on the Delmarva Peninsula. This year, they hope to see the flock of 11 birds make that trip without help. “When the freeze sets in, we believe this flock of healthy trumpeter swans will move south,” said Donielle Rininger, the lead biologist for Environmental Studies at Airlie, a nonprofit research organization which is in charge of the project.

Last fall’s southward migration encountered problems with the ultralight — the swans were faster than the plane making it difficult for the ultralight to maintain the “lead position” during the long flights.

So the biologists abandoned that technique and used a truck to move the swans about 40 miles a day. Each day, the ultralight would lead the birds into the sky on shorter flights so they could learn the local topography in the hope they would be able to repeat the route.

Previous experiments had shown that sandhill cranes could be taught migration routes by following trucks. But in experiments where geese were trucked and shown only part of the route, it did not lead to future migrations. Biologists won’t know whether the combination of trucking and ultralights works until this fall.

“If they make it back to the Bay, as I believe they will, it will be a tremendous breakthrough and will simplify this complex technique,” said William Sladen, director of Environmental Studies.

This spring, they birds gave mixed signals when it was time to fly north from their winter home at the Wildfowl Trust of North America near Grasonville, MD. Although they showed premigratory behaviors, the birds did not leave their Eastern Shore wintering grounds. So they were trucked to New York, where they spent the summer and fall.

Now, Rininger said, it’s a matter of waiting to see if they will make the return flight to the Bay. Exactly when that takes place depends on when the lakes and water holes in New York begin to freeze. “Trumpeters tend not to leave until they get frozen in and really have no choice but to go,” he said. “If they stay there until Christmas, I won’t be worried.”

Rininger said she would consider the experiment a success even if the birds only migrate part way back — as long as they migrate and find suitable open-water habitat. “I’m hoping they will make some movements,” she said.

Teaching the swans to migrate is the toughest part of trying to bring back a bird that was eliminated from the region more than two centuries ago. With large waterfowl, migration is usually taught by parents, but the birds raised here have no knowledge of historic migration routes, so humans have to act as surrogates.

If the swans don’t move this year, scientists will modify their techniques further in their attempt to teach the birds to migrate. If the birds prove to be non-migratory, they will be removed from the wild.

Birds migrate to take advantage of favorable climate and habitat conditions in different places at different times. If they stay in the same place all year and become “resident” birds, they can deplete local food sources or become nuisance species, as has happened with some Canada geese.

The winter and summer sites chosen for the swans are those thought to have been used by trumpeters before hunters wiped the birds out in this region more than 200 years ago, largely for their feathers and meat.

Once, nearly 100,000 trumpeters are thought to have wintered in the Bay region. Today, only about 19,000 of the birds remain in the continent, mainly in Alaska and the Pacific Northwest.

Historically, trumpeters were the largest waterfowl around the Bay. They can weigh up to 30 pounds, have an 8-foot wingspan, and can stand 4–5 feet tall. The have a long, convoluted trachea that produces their resonant trumpeting call.

Project scientists need the public’s help in tracking swans during migration. Anyone seeing them is asked to call a toll-free hotline, at 1-888-264-4728. All the swans are banded with U.S. Fish & Wildlife metal leg bands along with yellow plastic neck and leg bands with a unique code. If possible, callers should try to report the number, which can be read from a distance of about 15 feet, or with binoculars.