Thousands of tufted puffins in the Bering Sea are dead partly because of starvation and stress brought on by changing climate conditions, researchers say.

The puffins' food supply has been disrupted by changes in air and sea temperature, and in winter ice levels, according to a new study in the journal PLOS ONE.

Tufted puffins normally feed on krill and small fish; food that is now going to bigger predators than the orange-beaked seabirds.

One of the researchers, Julia Parrish, likens this change to going to the grocery store and not finding your usual goods.

"Except puffins are experiencing that throughout the entire Bering Sea," she said.

Starvation, she said, is inevitable given how much food puffins need. They normally eat about 30 to 50 per cent of their body mass every day.

"That's a lot of food, if you don't get any food in one day, you're in big trouble. If you don't get that in four days, you're dead," said John Piatt, a research wildlife biologist of the U.S. Geological Survey, who was not a part of the study.

According to Piatt, larger cold-blooded fish like cod normally eat about 0.1 to 0.2 per cent of their body weight every day. When the water temperatures increase, their metabolic rate rises by 30 to 50 per cent. This creates a bottleneck in the ecosystem where larger fish are eating more of the smaller fish that puffins normally prey on.

Increases in ocean temperatures have resulted in historically low sea ice extent records in the Bering Sea over the last five years, said Parrish.

When these changes occur, for certain species "if you're out of luck, you're out of luck," said Parrish.

Researchers found hundreds of dead puffins, including these from North Beach, St. Paul Full, Alaska, but believe thousands more have died. (Paul Melovidov)

Tufted puffins reside and mate throughout B.C. and Alaska, with big concentrations along the Aleutian Islands, in the Bering Islands and the Chukchi Sea. The researchers looked at puffins found on St. Paul Island, in the Bering Sea.

More than 300 carcasses found there were extremely emaciated from apparent starvation and stress.

When a bird dies at sea, it floats on the surface anywhere from four to 14 days, pushed along by the wind. After about two weeks, if the corpse doesn't wash up on St. Paul Island shore, it will sink.

Using wind data, researchers estimated the number of total number of dead puffins — during the four-month research period starting October 2016 — to be between 3,150 and 8,500.

'Flying' underwater

After their breeding season, puffins lose the feathers that allow them to fly, leaving them flightless for up to 40 days.

So after breeding, they migrate somewhere that usually has good access to food, Parrish said.

"They have to keep a little reserve through that migration because as soon as they get there, they drop flight feathers," she said.

The tufted puffins are able to "fly" underwater for their prey.

"When they drop their feathers, they still have enough wing area to fly underwater but they can't go as fast, so they won't be as good at getting fish," said Parrish.

Watch as these puffins fly underwater:

Parrish predicts more puffins will die, but says the changes so far do not indicate the species is going extinct.

An ecosystem is a finely tuned machine, every part dependent on the others to work as a comprehensive whole, she said.

"I think people will think climate change will make everything go away," she said. "That's not the case, but it will make a lot of things shift, and we will see a lot of mortality, and it will go on for much longer than our lifetimes."