Editor's note: the above video first aired in January 2018
Since March 17, more than 50 trumpeter swans have been found dead or dying south of Monroe and into north King County.
The Daily Herald reports more than two dozen of the dead came from Crescent Lake near the Snoqualmie River, a major night roost for swans this time of year.
The state Department of Fish and Wildlife and advocates for swans have retrieved many of the birds to study the swans' livers and gizzards to confirm what's causing their deaths.
State biologist Daniel Zimmerman says the number of swan deaths has been unusual with some 10 deaths in a more typical year. He says lead poisoning is suspected although the winter snowstorms could have played a role.
Despite the deaths, Zimmerman says area trumpeter and tundra swan populations have increased more than 14 percent overall during the past four years.