(CALLAM COUNTY, Wash.) — More than 50 trumpeter swans have died in the past two weeks in northwest Washington, possibly due to lead poising, experts say.When Martha Jordan, the director of the Northwest Swan Conservation Association (NSCA), went on a routine survey at Crescent Lake on March 10, the swan population distribution was relatively normal. When she returned a week later, she noticed multiple carcasses and feather piles — remnants of a bird after they’ve been eaten by a predator.”I knew I needed to go out on my boat with my dog to search for more,” said Jordan.According to Jordan, almost all the swans have classic symptoms of lead poisoning: weight loss, swelling, a paralyzed nervous system that makes walking and flying difficult, and trouble holding their heads up.With 40 years of experience dealing with swans, Jordan said the event “blindsided everybody.”Though this type of die-off is common in other areas, it’s rare for this region, she said.Part of the reason could be due to weather. A rare snow storm hit the Pacific Northwest in February, which pushed a lot the swans and other animals into areas they don’t normally go. Those areas might have sources of lead, according to Daniel Zimmerman from the Washington State Department of Fish and Wildlife.March is when the swans start to migrate to their breeding ground, and those that remain are usually single birds, as swans are known to have strong pair bonds.On one of her recent survey trips, Jordan saw a pair of swans who stayed behind, one swimming back and forth to its partner who was clearly sick and struggling.”The sick one made horrific sounds, sounds I’ve never heard a swan make, I just had to turn away because at that point there’s nothing I can do.”The next day Jordan saw one of them had died and the mate stayed by its side.”It’s hard to watch. You’re witnessing the lives of these birds,” she added.Lead shot has been banned from waterfowl hunting nationwide by the U.S. Fish and Wildlife Service since 1991, but there are lead shots still in the environment from hunting that took place before the policy and clay target shooting in the area.”That’s one of the things that’s very hard. We don’t exactly know where they’re getting all of it [lead],” Zimmerman told ABC News.It takes three to four weeks for symptoms of lead poisoning in the birds to show up, according to Zimmerman. By the time the birds are dying, it’s not clear where the lead came from.As a supporter for legal hunting, Jordan is urging people to use nontoxic ammunition.”There’s no good excuse to not,” she said. “Often people say nontoxic ammunition is too expensive, even though it costs hundreds of thousands of dollars to deal with the environmental consequences, taxpayer dollars, and they’re saying it’s too expensive for them?” said Jordan.NSCA is working closely with Washington Department of Fish and Wildlife to discuss next steps, including cleaning up the carcasses so there’s no secondary poisoning, placing poles where there is lead to discourage landing or feeding in the area and possibly track the swans if there is enough funding.Copyright © 2019, ABC Radio. All rights reserved.