BELLINGHAM– More than 60 trumpeter swans found dead in the last few weeks northeast of Bellingham appear to have succumbed to lead poisoning, according to Washington Department of Fish and Wildlife (WDFW) wildlife biologists.
Although the source of the lead has not been confirmed, the swans may have been poisoned by ingesting lead shotgun pellets that came to rest on lake bottoms and the ground, said Lora Leschner, regional wildlife manager in WDFW's North Puget Sound regional office in Mill Creek.
The dead swans are being collected promptly so that bald eagles do not feed on the swan carcasses and suffer secondary poisoning. Volunteers and wildlife rehabilitators are working with WDFW to recover the dead swans.
Lead shot has been illegal for waterfowl hunting in western Washington since 1986 and nationally since 1991. Lead shot still is legal for use by upland bird hunters throughout the state, however.
Although no connection has been established between the use of lead shot by state upland bird hunters and the recent swan deaths, the Washington Fish and Wildlife Commission already was scheduled to decide in its April 7 and 8 meeting in Yakima whether to phase out the use of lead shot on pheasant release sites where waterfowl are present in significant numbers, to restrict lead only on release sites where problems are documented, or to leave the current regulations in place.
In Canada, hunters have been allowed to use lead shot in many areas until this past year. WDFW wildlife managers have contacted Canadian wildlife officials about the swan die-off and are working to try to determine the chief source of the lead and whether swan deaths have occurred in Canada.
If the source of the lead can be found, action can be taken to drive swans away from problem areas.
Lead shot can pose particular risks to waterfowl and other wildlife in wet areas and in areas where upland bird hunters concentrate, such as state pheasant release sites. Swans can become poisoned as they forage in fields or on lake bottoms and accidentally ingest the spent shot.
All the dead swans have been examined and show signs of lead poisoning, said Mike Davison, WDFW district wildlife biologist. Several also have been x-rayed, revealing lead shot in their gizzards.
Only one or two swallowed lead pellets are enough to kill a swan, Leschner said. Even if the exposure isn't fatal it can weaken birds and cause them to succumb to other ailments such as aspergillosis, a lung ailment caused by a fungus present on decaying corn and other grain, she added.
The dead birds are among a wintering population of about 1,000 trumpeter swans in Whatcom County. Another several thousand swans are present in winter months in Skagit County. Some swans die each year from lead poisoning and aspergillosis; the last large die-off was in 1992, Leschner said.