In the storm debris littering a Washington State shoreline, Bonnie Wood saw something grisly: the mangled bodies of dozens of scraggly young seabirds.

Walking half a mile along the beach at Twin Harbors State Park on Wednesday, Wood spotted more than 130 carcasses of juvenile Cassin's auklets—the blue-footed, palm-size victims of what is becoming one of the largest mass die-offs of seabirds ever recorded.

"It was so distressing," recalled Wood, a volunteer who patrols Pacific Northwest beaches looking for dead or stranded birds. "They were just everywhere. Every ten yards we'd find another ten bodies of these sweet little things."

Cassin's auklets are tiny diving seabirds that look like puffballs. They feed on animal plankton and build their nests by burrowing