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Update, January 15, 2020: Since this story was published in 2016, scientists have estimated that 1 million Common Murres died during this mass mortality event—the largest known die-off of a single bird species ever. The birds died from starvation after a long-lasting marine heat wave known as ‘the blob’ squeezed the ecosystem’s food supply. “We believe that the smoking gun for Common Murres—beyond the marine heat wave itself—was an ecosystem squeeze: fewer forage fish and smaller prey in general, at the same time that competition from big fish predators like walleye, pollock, and Pacific cod greatly increased,” says author Julia Parrish from the University of Washington. Marine heat waves are growing in scale and frequency with climate change. .

Anyone braving the cold beaches of Alaska in the last few weeks would be met with a strange sight—tens of thousands of Common Murres, bowling-pin-sized seabirds, have been washing ashore dead along the coast, from the Prince William Sound to Kodiak Island (and beyond). Faced with one of the biggest die-offs in recent memory, wildlife biologists are wondering whether it’s part of the natural cycle, or a sign of something more ominous.  

Die-offs, also known as wrecks, are fairly routine among seabirds like murres, auklets and shearwaters, says Heather Renner, supervisory wildlife biologist for the Alaska Maritime National Wildlife Refuge in Homer, Alaska. Alaska has seen several in the past few decades, though the largest came in 1970 when surveys found as many as 3,400 dead murres per mile of beach.

This die-off is unusually large, although the best estimate Renner can make is that tens of thousands of birds are involved. Also strange—and more worrisome to biologists—is that it follows a complete and inexplicable breeding failure of Common Murres (and, in one colony, closely related Thick-billed Murres) in parts of Alaska. (No Thick-billeds have been found dead, Renner said, perhaps because they may winter farther from land.)

"For the 30 years or so that we've been monitoring them, we've never had complete reproductive failure at most of these colonies,” Renner says. “It wasn't everywhere, but at a bunch of these colonies there was just nobody home—the cliffs were bare."

How it Started

The dead birds started washing up during the summer, tracked by volunteer monitors taking part in the Coastal Observation and Seabird Survey Team () program, Renner says. When thousands of dead murres were reported from Kodiak Island in August (along with 18 dead fin and humpback whales), biologists started to take notice.

Then a massive storm, with warm, southerly winds exceeding 120 mph, came roaring across Alaska in late December. It scattered thousands of dead murres along Prince William Sound and the Kenai Peninsula. Scavenging Bald Eagles "are having a heyday,” says Renner, who lives by the beach in Homer. “They're leaving murre bits all over. I've had them dropping them in my hot tub."

The Race to Rescue Survivors

Near Denali National Park, 150 miles from the ocean, four-time Iditarod champion Jeff King was running his sled dog team when he rescued a couple of murres—among many that flabbergasted birders, mushers, and homeowners have found floundering in the deep snow as far inland as Fairbanks, another hundred miles north. Rescued birds were generally emaciated and weak, but even healthy murres can't easily take off from land, where they are at the mercy of predators and the elements.

"They were kind of everywhere," says Jill Boelsma of the Denali Education Center. Boelsma’s enclosed home porch became a temporary murre clinic for birds, including those King rescued, waiting to return to sea. She turned to ̽����ѡ seabird expert Steve Kress (of Project Puffin) for advice, and to her neighbors for help. Dog mushers provided bales of clean straw to cover the floor; halibut fishermen gave up their frozen bait herring to feed the birds— the perfect nourishment.

"Once we got some calories in them, they got pretty feisty, pretty fast," Boelsma says.

About 100 murre carcasses have been sent for testing to the National Wildlife Health Center in Madison, WI, Renner said. All showed signs of starvation, and none have tested positive for toxins, or for viruses like avian influenza. "The consensus is it's almost certainly food-related," she said.

Could the Blob Be to Blame?

Although it's too soon to say, Renner and other seabird biologists suspect the breeding collapse and the murre die-off could be tied to abnormally warm sea surface temperatures. Since late 2013, a pool of water several degrees Fahrenheit above average—dubbed "" by  and  alike—has dominated the North Pacific, altering cold-dependent marine food chains. Last winter, dead Cassin’s Auklets started washing ashore as far south as California, likely suffering from the disrupted food chain.

"With the Blob, and water temperatures several degrees above average, there have been lots of strange things going on," Renner says. The Blob predates the warm temperatures the current El Niño is producing in the Pacific, oceanographers say, and is not related to it; nor does it appear to be directly linked to global warming. It , in which the Pacific naturally fluctuates between cooler- and warmer-water conditions, but the Blob has set all-time records for heat, and could be a hint of future conditions.

The numbers of dead murres are high enough that there could be an effect on the population, says Renner, particularly since the die-off will likely continue through the winter. But with Alaskan murre populations in the millions, Renner says she is “not super worried.”

“I don't expect that we're going to start seeing a big population decline," she says.

With rehab facilities overwhelmed, USFWS isn't asking the public to rescue any more murres, but they are encouraging people to report dead seabirds (information on how to do that is ), and to take part in the COASST surveys.