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Species that edges out trumpeter and tundra swans spotted at wetlands

by: COURTESY PHOTO: JACK WILLIAMSON - Mute swans, an invasive species that has migrated to Fernhill Wetlands in Forest Grove from the Eugene area, are trouble, experts say.When 10 beautiful swans surprised veteran birdwatcher Phil Kahler June 16 at Fernhill Wetlands, he didn’t realize they posed a threat to other waterfowl — and even people.

Kahler, who has visited Fernhill regularly to observe winged wildlife since he moved to Forest Grove 20 years ago, had trouble identifying the swans at first.

“We usually get tundra swans and sometimes trumpeters, but never in June,” Kahler said. “Turns out, they don’t belong here.”

The orange-billed birds were mute swans, an invasive species from Europe that edges out native waterfowl and is on Oregon’s “100 worst” invasive-species list.

Elsewhere in the country, they’ve taken over some areas. In Chesapeake Bay, for example, a feral population of 200 swans has grown to 10,000.

Mute swans consume large amounts of vegetation that migratory waterfowl — including the native tundra and trumpeter swans — depend on.

Rick Boatner, invasive species coordinator for the state, said each mute swan eats eight to 10 pounds of submerged vegetation a day.

With 10 swans, Boatner said, “that’s 100 pounds” — a devastating amount, especially given that unlike their native brethren, mute swans don’t migrate, so the daily gobble goes on year-round.

In addition, mute swans behave aggressively toward humans, said Kahler, a science teacher whose students at Tualitin Valley Junior Academy in Hillsboro take part in birding activities at Fernhill. A friend of Kahler’s was once attacked by a mute swan. The 30-pound birds have powerful wings that can span up to 8 feet and deliver painful blows.

In the past, golf course and park owners in Oregon have legally stocked neutered and pinioned swans on private ponds for visitor enjoyment. But ODFW now forbids importation of the species, so those birds should eventually die out.

Kahler and Boatner suspect the flock at Fernhill flew south from British Columbia, where a large population lives unmitigated. Photos taken by Kahler and other birders show the swans flying, so their wings are unpinned.

Kahler posted his initial swan sighting on birder blogs, including Oregon Birders Online (OBOL), sparking a lively statewide discussion. Harry Nehls of Portland reported that a local mortuary used to keep a flock. Biologist Cathy Nowak of LaGrande contacted ODFW personnel. As many as six others offered opinions and reported sightings — most recently Jack Williamson of West Linn, who saw 11 mute swans at Fernhill Thursday, June 27.

“Everybody’s wondering if Fish and Wildlife is going to do something about it,” Kahler said.

Boatner said ODFW employees will wait until the swans begin molting in a few weeks before trying to remove them. During the month-long molt, the swans are unable to fly as far and may be easier to capture. He hopes to funnel the flock into a holding area, then remove and euthanize them during July or August.

He said private individuals could obtain swans in the Fernhill flock if they agree to properly pin and neuter the birds. But the neutering procedure for male swans is high-risk, Boatner said, and few veterinarians will perform it.

Surveys counted 700 mute swans along the Pacific Flyway in 1996 and only 42 in 2009, so local efforts to control the population seem to be working.

But Kahler said people already admire the swans, which might make their “removal” more controversial. “We want (ODFW) to do something before people get attached to them,” he said.

Boatner agrees. “They get political real quick, these birds,” he said. “They’re gorgeous.”

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