Why is the beach covered in dead birds?

Many visitors to Oregon's coast over the holidays were greeted with the disturbing sight of dead seabirds.

On Dec. 21, on the beach at Seaside, more than 50 dead birds washed ashore, most of them Cassin's auklets.

On Dec. 26, Robert Ollikainen, of Tillamook, found 132 dead birds on the beach there, including 126 Cassin's auklets.

"It was pretty dramatic," Ollikainen said.

On Dec. 27, Dave Miller counted 15 dead Cassin's auklets at Moolack Beach. The next day, he found more at Beverly Beach.

"I estimate there were probably 30 to 50 per mile," said Miller, who grew up in Newport and now lives in Camas, Wash. "I've never seen that many before."

It's normal for some seabirds to die during harsh winter conditions, especially during big storms like the one that occurred Dec. 21, said Julia Burco, wildlife veterinarian for the Oregon Department of Fish and Wildlife.

But a mass die-off of Cassin's auklets — a "wreck" in birding lingo — has been going on along the entire West Coast since October, and no one knows exactly why.

Mass die-offs of the small, white-bellied gray birds have been reported from British Columbia to San Luis Obispo, Calif.

But Oregon's north coast seems to be the epicenter, said Phillip Johnson, executive director of the Oregon Shores Conservation Coalition.

"We've been receiving a lot of reports in the last couple weeks," Johnson said.

There also have been reports of live but struggling Cassin's auklets on beaches since November.

Oregon State University tested some of the dead birds from Seaside. Preliminary reports indicate they starved to death, Burco said.

"It doesn't look like a toxin," she said. "It's more likely due to weather and food supply."

But why are the birds starving?

Some experts speculate the die-off is the result of a successful breeding season: If the population grows rapidly, a certain percentage of young won't survive.

Others point to climate change:

Unusually violent storms may be pushing the birds into areas they're not used to, or are preventing them from foraging.

Or, a warming and more acidic ocean could be affecting the tiny zooplankton, such as krill, the birds feed upon.

"The suggestion is that the ocean for some combination of reasons is less abundant for their food sources," Johnson said.

The U.S. Geological Survey's National Wildlife Health Center in Wisconsin is conducting additional necropsies on dead Cassin's auklets, Johnson said.

And the University of Washington's Coastal Observation and Seabird Survey Team (COASST) is studying the die-off.

"To be this lengthy and geographically widespread, I think is kind of unprecedented," Johnson said. "It's an interesting and somewhat mysterious event."

tloew@statesmanjournal.com, (503) 399-6779 or follow at Twitter.com/SJWatchdog