ROSE LAKE — Hundreds of tundra swans were feeding in the floodplain off Highway 3 near Killarney Lake on Thursday.

They appeared healthy, some floating close to shore, most farther out, and none seeming to be bothered by admirers who stopped to watch them on a sunny afternoon.

“That’s quite a sight,” said Mary Ralston, a visitor on a scenic drive.

A happy one, too.

This year’s return of the swans to the Lower Coeur d’Alene River Basin is going well, with just four mortalities, an improvement over 2022 when more than 350 deaths were reported, due primarily to their food source being contaminated by a century of mining waste.

“It’s pretty opposite of last year,” said Sarah Emeterio, U.S. Fish and Wildlife biologist. “That’s fantastic news.”

There are reasons for the reduced deaths.

Last year, the migrating swans arrived in large numbers early, starting in late February, and stayed late.

This year, far fewer of the graceful white birds have made an appearance.

In the first week of March 2022, 5,077 swans were counted. For the same week this year, the tally was 132.

As of last week, the total FWS swan count was 8,698. Last year’s count was more than 24,000, a record.

The reason for fewer swans has to do with favorable conditions — cool, wet, with abundant plants to eat — in northern and central California, where they reside before heading to North Idaho.

The swans had little incentive to move on, Emeterio said.

“Where they’re wintering has been fantastic,” she said.

Last year, there were drought conditions in California, which led the swans to depart early for the lower Coeur d’Alene River Basin.

As well, when they arrived, many were skinnier, in a "compromised condition," Emeterio said. This year, they’re bulkier, thanks to a good diet before departing California.

Another factor, much of the basin was still frozen when the swans arrived last year. They found food in sites more contaminated with mining waste.

“Those that were open were the hotter areas,” Emeterio said. “They just had greater exposure than the ones that came in this year."

This year’s conditions in the basin are not the best ever, with a dry spring, but they’re not terrible, either. The lower basin had thawed, giving the swans a wider area to feast.

According to Idaho Fish and Game, mining waste was discharged into the Coeur d’Alene River and its tributaries for much of the 20th century.

“This caused metals like lead to accumulate in many of the marsh soils along the river,” a 2019 Fish and Game report said. “Around 95% of wetland habitat in the lower Coeur d’Alene River Basin contains lead levels toxic to swans and other waterfowl.”

Wildlife officials say tundra swans are vulnerable because they burrow deep into the mud to feed on roots and tubers, increasing their chances of eating contaminants, like lead, in the soil.

There have been successful efforts to clean things up.

The Schlepp Wetlands Restoration Area in the lower basin has over 400 acres of a clean and productive wetland habitat used by swans.

Emeterio said while many swans will still arrive on the lower Coeur d'Alene Basin, more will be leaving as they head to Alaska, where they need to arrive by mid-May.

“They have to go or they’ll miss the window for breeding,” she said.