Biologists from the Washington Department of Fish and Wildlife (WDFW) and their Canadian counterparts are accelerating a coordinated effort to find out why trumpeter swans are still dying from lead poisoning, even though lead shot has been banned in the United States and Canada for years.
A team of biologists from WDFW and the Canadian Wildlife Service are trying to trap about 50 trumpeter swans and fit them with radio-transmitting collars to monitor them during their annual migration. Ground crews will be able to pinpoint exact habitats used by the swans and systematically check those areas for concentrations of spent lead shot and develop removal plans.
The first trumpeter swan fitted with a radio-transmitting collar will be released into the Wiser Lake wildlife site, south of Lynden, just off State Route 539, at 2 p.m. on Friday, Nov. 16. This particular bird, a sub-adult female, was found shot and severely injured in northwestern Washington last winter and has been rehabilitated at the Pilchuck Valley Wildlife Rehabilitation Center.
"We have lost probably 200 to 300 trumpeter swans to lead poisoning over the last few years," said WDFW wildlife biologist Mike Davison, who is heading the trumpeter swan research effort. "This is a catastrophic die-off."
A few individuals are probably still using lead shot. However, the agency is operating on the premise that most of these birds have been getting lead poisoning from historically deposited lead, and not from current illegal hunting. The swans, with their long necks, are likely reaching these shallow underwater areas where spent lead shot is still present.
"As far as hunters are concerned, we're getting good compliance with the non- toxic shot requirements," Davison said. Lead shot was banned in the United States in the mid-1980s; Canada banned lead shot in the mid-1990s.
The overall health of the trumpeter swan population in Washington state is strong, but the fact that swans are still dying from lead poisoning is a concern to WDFW. Nearly three-quarters of the trumpeter swans that migrate along the west coast's great Pacific Flyway winter in Washington state, mainly in Whatcom and Skagit counties. More than 1,000 trumpeter and tundra swans overwinter in Whatcom County alone.
"The birds are picking up lead in numbers and volumes that couldn't be found randomly in a number of sites, so we think there are possibly a few key areas that have very high lead concentrations that are poisoning the swans," Davison said.
The agency has aggressively sampled various areas the trumpeter swans use in Washington state, and none have been found to have high lead concentrations.
"We found one area of interest in British Columbia that's just across the border and falls within the flight radius of the birds we're studying with unusually high levels of lead," Davison said, adding that biologists will return to the lake next summer for a more intensive study.
Just one or two ingested lead pellets can kill a bird, and it usually takes only 10 days from ingestion until a bird displays visible symptoms of lead poisoning being displayed. How long the lead takes to kill the bird depends on a number of factors, but it's usually a matter of three weeks to six weeks.
Trumpeter swans are off-limits to hunting in both the U.S. and Canada. With their bright white plumage and large size, the swans are one of the most visible bird species in the region and attract big crowds to their traditional wintering grounds in Skagit and Whatcom counties. The birds arrive generally in late October and will stay in northwestern Washington over the winter before beginning their northward migration in April. They nest in central Alaska and points north.