The birds, whose wingspans can reach 8 feet across, need open, fresh water that’s not too deep, so they can feed off the bottom. They usually migrate south in winter to find lakes that aren’t frozen over. Mating for life, they often nest in the same area where the female, known as a pen, was born.

Coming in for a landing in winter, the birds sound like a group of enthusiastic 4-year-olds with party horns. But once situated, they rarely make much noise, Ms. Smith said.

Trumpeter swans had been so plentiful in Ontario in the early 1700s that Antoine de la Mothe Cadillac, who commanded the French settlement that became Detroit, said they “might be taken for lilies.” But settlers and trappers wiped them out. European settlers in North America killed the swans for food, and turned their down-covered skin into powder puffs for cosmetics and their feathers into quill pens, said Gary Ivey, a past president of the Trumpeter Swan Society. John James Audubon, the famous naturalist, preferred trumpeter swan feather quills to any others, he said.

The last wild trumpeter swan in Ontario was recorded shot in 1886.

“Our heritage was missing from Ontario altogether,” said Harry Lumsden, who retired from the Ontario Ministry of Natural Resources, in 1988, six years after starting the restoration effort there. At age 95, Mr. Lumsden continues to work for trumpeter swans nearly every day. “I’ll do anything for swans,” he said by phone.

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The Ontario reintroduction effort started with wild collected eggs from Alberta, which were placed under mute swans, a related species, to hatch. Mr. Lumsden found “cooperators” — like Ms. Kingdon and her parents — who had suitable properties and were willing to host pairs of breeding swans. In the fall, the fledglings would be relocated for the winter and then released in suitable places in the spring. In 1993, swans hatched in the wild in Ontario for the first time in more than a century.

There were so few birds that they were quite inbred, and many of their eggs didn’t hatch, Mr. Lumsden said. But when Michigan cut the budget for swan reintroduction in 1992, it gave Ontario the 50 Alaskan eggs from the state’s program. Three-quarters of the eggs began hatching, instead of only half.