The birds have been clobbered by an unusual algae bloom stretching from the northern Oregon coast to the tip of the Olympic Peninsula in Washington state.
"This is huge," said Julia Parrish, a marine biologist and professor at the University of Washington who leads a seabird monitoring group. "It's the largest mortality event of its kind on the West Coast that we know of."
The culprit is a single-cell algae or phytoplankton called Akashiwo sanguinea. Though the algae has multiplied off the coast of California before, killing hundreds of seabirds, the phenomenon has not been seen in Oregon and Washington, and has never occurred on the West Coast to this extent, Parrish said.