PORTLAND — The killer foam that hit Northwest seabirds has subsided but conservationists are worried about a death toll they say numbers in the thousands.

The first algal foam that hit Washington's Olympic Peninsula in mid-September claimed more than 10,000 scoters, or seaducks, said Julia Parrish, a University of Washington marine biologist and seabird specialist. She says that toll, mostly surf scoters and white-winged scoters, amounts to 5 percent to 7 percent of their overall population on the West Coast.

"I don't think it will knock the population back for years," Parrish said. "But at least with surf scoters — a species that's in decline — conservation scientists are rather concerned about it."

She thinks thousands more seabirds, including many red-throated loons, were killed in the second wave of foam off southwest Washington's Long Beach Peninsula about two weeks ago.

The foam has been linked to the bloom of a single-cell phytoplankton, or algae — called Akashiwo sanguinea — that hasn't posed a problem in the Northwest until now. Scientists suspect it made the most of a combination of warm water and low salinity. Winds blew the bloom toward shore where it was whipped by the surf into sticky foam that stripped the birds of their waterproofing.

There is some good news; several hundred rescued birds are being released.

This week, about 200 have been released by the International Bird Rescue Research Center north of San Francisco.

"To see them released and returned to the wild is a wonderful feeling for all the volunteers who've worked so hard to make this happen," center spokesman Paul Kelway said.

The research center accepted 450 seabirds from the Wildlife Center of the North Coast near Astoria, which was overwhelmed with birds from the nearby Long Beach Peninsula.

Almost 100 went to PAWS Wildlife Center north of Seattle and another 75 stayed at the facility near Astoria.

"We kept the worst of the birds because they wouldn't have made it through the trip," said Sharnelle Fee, director of the Wildlife Center of the North Coast.

Initially the birds were given warm fluids and food. Once they gained strength, they were washed in tubs of warm, soapy water.

The clean birds were put in plastic cages with netting on the bottom, giving them a soft surface not unlike the ocean.

To dry them, the cages were suspended under pet dryers circulating warm air.

The birds were then placed in preening pools to finish their rehabilitation.

The Bay Area center could free more birds next week, and the center near Astoria could stage releases as well.