It may not sound like much to most people, but some biologists are hoping that a small ultralight aircraft is playing a tune that will bring back the past.

Sometime this fall, they hope the ultralight will lead a band of trumpeter swans, which have been reared to follow the aircraft's engine since before they were hatched, on a flight from Virginia to Maryland's Eastern Shore.

If the seven birds follow, it will be the critical first step in an effort to restore a species to the Bay region that was wiped out in the Eastern United States more than a century ago.

Trumpeter swans grow to be 60 inches long and are the largest waterfowl in North America. But they were literally shot out of the sky so long ago that many people don't know they were even here in the first place. The swan is not included in Audubon guides to Eastern United States birds.

Project supporters see the return of the trumpeters as a boost to the region's native biodiversity and view the bird as a spectacular flying ambassador-full- grown trumpeters can have a 9-foot wingspan and weigh 35 pounds-that will help educate the public about the importance of protecting wetlands on a regional basis.

"When you look at wetlands and think about species like the trumpeter swan, you might think about our western plains and the bison," said Bob Ferris, director of the species conservation division of the environmental group, Defenders of Wildlife. "Here we have an opportunity-for our eastern wetlands-to replace the ecological equivalent of a bison species by replacing the trumpeter swan."

The privately funded, $750,000 project is a joint effort of Defenders and the research organization, Environmental Studies at Airlie Center near Warrenton, Va.

Reintroducing the birds is no problem, biologists say. The trick is to teach the swans to follow a migratory flight path -a job typically done by their parents. Because there are no migratory trumpeters in the East, the only ones who can teach the young birds to migrate are humans.

That is where the ultralight comes in. Biologists have been "imprinting" the sound of humans and ultralights on the birds, hoping they will associate-and ultimately follow-the people and plane just as they would have followed their own parents.

"They started playing a recording of the ultralight while [the swans] were still in the eggs," Ferris said. "Normally, the young of these birds would be hearing some sort of sounds through the eggs, in the sense that the parents would be around vocalizing. And trumpeter swans, as their name suggests, are vocal birds. It's one of those very moving sounds in nature."

Since they were hatched this spring, seven young swans have been learning to follow humans, an ultralight and a small, unmanned, remote-control aircraft. Sometime in late October or November, Environmental Studies biologist Gavin Shire will use the ultralight to guide the birds on a 100-mile trip from Airlie to a farm managed by Defenders near the Blackwater Wildlife Refuge on Maryland's Eastern Shore.

Next spring, if the birds migrate back to the Airlie "breeding grounds," the first phase of the experiment will be considered a success. At that point, the biologists will turn their eyes north, hoping to raise the next batch of young at a historical breeding ground for the swans. Ferris said a wildlife preserve in New York between Rochester and Buffalo, where records show trumpeters nested in the mid-1800s, is the likely candidate for the breeding ground site.

Using the same ultralight technique, the biologists hope to select a safe, easily identifiable route-probably down the Susquehanna River-for those birds to migrate to their Chesapeake wintering ground next fall.

If the birds return to New York on their own the next spring, the scientists will bolster the flock with additional birds and lead another migration that fall. After that, plans call for the emphasis to switch to monitoring the birds.

The ultralight technique, popularized in the movie "Fly Away Home," was originated by Canadian ultralight enthusiast and metal sculptor William Lishman, who trained a flock of Canada geese to fly behind his ultralight as their surrogate parent. In 1990, he teamed up with William Sladen, of Environmental Studies, and in 1993 they completed the first ultralight-led goose migration from Ontario to Airlie, Va., a distance of 420 miles.

Two other "migrations" led by the ultralight have taken place since then. After the initial migration, follow-up studies found that 89 percent of the birds continued the annual flight on their own. By contrast, experiments conducted with two flocks of geese "migrated" by truck failed to result in any birds returning on their own.

The migration part of the project is critical, biologists say, because if the birds do not learn to leave the Bay region in the summer, they would create the same kinds of ecological problems caused by mute swans, a species that was introduced to the area and does not migrate. During the summer, the mute swans interfere with other summer nesting birds and rip up beds of Bay grasses that provide important habitat for other species.

"We're not really keen on having a resident population," said Bill Harvey, a biologist with the Maryland Department of Natural Resources, which is supportive of the reintroduction effort. "It would be the same story as the mute swans. They would be here at a time of year when they historically weren't here. You would have the same trouble with feeding on grass beds during the growing season, and things like this. So we're interested in restoring this as a migrant population."

Trumpeter swans were heavily hunted since the early days of colonization; their feathers were used for quill pens and fashionable hats, and their flesh was used for food. They were wiped out on the Delmarva Peninsula two centuries ago, and from the rest of the East shortly thereafter. By 1932, only 69 trumpeter swans were known to exist in all the lower 48 states.

Since then, conservation efforts have helped to increase the overall trumpeter population to more than 19,000 birds, mostly in the Pacific Flyway. Biologists hope the species will be better protected through efforts to restore it in other parts of its historic range. It has been reintroduced in the Midwest, but those birds do not migrate.

Still, Ferris said, the current number of birds "doesn't seem near enough." Historically, he said, there were probably about 100,000 trumpeter swans that wintered between Delaware and Northern Florida along the Atlantic Flyway.

He said success with the trumpeters may help other birds, such as the endangered whooping crane. The ultralights can be used to not only train the birds to migrate, but could help select destinations that protect them from various threats, such as pollution or encroaching development.

The technique may also offer some relief to this region's mushrooming problem with resident, or nonmigratory, Canada geese. Their rapidly expanding population is overrunning parks, lawns and golf courses during the summer. Those birds should be nesting in the Arctic at that time of year, but the resident birds stem from captive flocks that never learned to migrate.

"That's something that we've got our eye on," Ferris said. "If we can figure out ways of doing this on a fairly grand scale, how can that be used to solve some of these nonmigratory goose problems?"