A successful migration by 10 trumpeter swans from New York to the Chesapeake Bay was marred when one of the rare birds was shot and killed a week after completing the flight.

State and federal wildlife agents are investigating the Jan. 28 incident. A local resident spotted the dead swan floating shortly after noon in Cabin Creek near the Horsehead Wetlands Center on Maryland’s Kent Island.

X-rays revealed the swan had been shot with a pellet rifle. “We believe that this was not the act of a hunter, but one of vandalism,” said Donielle Rininger, lead biologist with Environmental Studies at Airlie, which is heading a trumpeter swan reintroduction experiment.

All the swans participating in the experiment were wearing bright yellow collars and a transmitter. A reward is being offered for information leading to the conviction of the person who shot the swan.

Anyone with information can contact the U.S. Fish and Wildlife Service at 410-228-7991, or the Maryland Natural Resources Police at 410-820-1314.

Trumpeter swans were hunted to extinction in this region of the country more than 200 years ago by people seeking their meat and feathers.

The swan that was shot was part of an experiment aimed at reintroducing a migratory population of the birds to the region.

The shooting dampened what had been an otherwise successful attempt to use an ultralight aircraft to lead the young swans, which had been hatched last summer in the wilds of Alaska, from western New York to the Eastern Shore.

The 330-mile journey began Dec. 29 and was completed Jan. 18 when they reached the Horsehead Wetlands Center, which is managed by the Wildfowl Trust of North America, where they are spending the winter.

The hope is, that after having made the migration behind the ultralight, the swans will return on their own to New York in the spring.

Ensuring that the reintroduced birds become migratory is a critical part of the project. Birds migrate to take advantage of food supplies in different regions at different times of the year.

If they do not migrate, their year-round presence could make them a nuisance species, as has been the case with large summer flocks of “resident” Canada geese that overrun parks, fields and golf courses in the region.

Officials said they would not pursue reintroduction if they cannot successfully teach the birds to migrate on their own between their historic summer breeding grounds in New York and their historic wintering grounds on the Bay.

Usually, migration by large waterfowl is taught by parents. But because the swans were wiped out from the region two centuries ago, there are no adult birds to teach a migration route, so humans have had to act as surrogates.

Biologists have been experimenting with ways to teach birds migration routes for four years, and last fall’s experiment was the most successful to date.

Once, nearly 100,000 trumpeters are thought to have wintered in the region. Today, there are only about 19,000 birds on the entire 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. They have a long, convoluted trachea that produces their resonant trumpeting call.