Between October 2016 and January 2017, the carcasses of hundreds of severely emaciated seabirds, mostly tufted puffins, washed onto the beaches of St. Paul Island, off Alaska.

Not all birds that die wash up on a beach and are discovered. So the researchers ran an analysis and estimated that between 2,740 to 7,600 tufted puffins died during that time.

Upon examining the carcasses, the researchers found that the birds had most likely died of starvation linked to shortage in prey triggered by climate change and a warming ocean.

On the remote island of St. Paul, located in the Bering Sea off the coast of Alaska, more than 350 severely emaciated carcasses of sea birds, primarily tufted puffins, washed ashore between October 2016 and January 2017. Now, new research suggests that climate change may have been to blame.

The Aleut Community of St. Paul Island, in collaboration with researchers of the Coastal Observation and Seabird Survey Team (COASST), a citizen science project housed at the University of Washington, have been regularly conducting monthly surveys to record dead birds that wash onto the island’s beaches. Beginning in October 2016, though, the residents observed something odd: where earlier they rarely came across carcasses of tufted puffins (Fratercula cirrhata), now there were nearly 300 of them in a span of just four months. During the previous decade, between June 2006 and September 2016, the teams had come across only six puffin carcasses.

Not all birds that die end up on a beach and are discovered. So the researchers ran several wind simulation experiments, based on known locations of the bird carcasses and wind conditions observed when the birds had washed ashore, and estimated that between 2,740 to 7,600 tufted puffins died during that time. Since an old estimate of the tufted puffin population on the Pribilof Islands — St. Paul is one of four of these islands — puts their number at only 7,000 breeding individuals, researchers say that the dying birds likely also came from other colonies.

“Island residents collected high quality data in real time and provided COASST with a detailed context for their analysis,” study co-author Lauren Divine, from the Aleut Community of St. Paul Island Ecosystem Conservation Office, said in a statement. “Without the positive and mutually beneficial relationship built over years of collaboration, this massive die-off of Tufted Puffins would have gone unreported in the scientific community.”

Upon examining the carcasses, the researchers ruled out infections and toxins as causes of the puffin die-offs. Instead, they found that the birds had likely died primarily of starvation. All the carcasses the researchers examined looked extremely thin and weak, with atrophied flight muscles and very little body fat. The majority of the dead puffins were also regrowing their flight feathers in an energy-intensive process called molting.

Tufted puffins that breed in the Bering Sea eat fish like juvenile pollock, capelin, and pacific sandlance, and invertebrates like squid, which in turn feed on ocean plankton. But thanks to climate change and warming oceans, food is in short supply now.

In recent years, rising atmospheric and sea temperatures have resulted in reduced winter sea ice in the Bering Sea. This in turn has caused declines in populations of fish and planktons and changed their distribution.

“There’s a shift to smaller and less energy intense species,” Julia Parrish, a professor at the University of Washington and the executive director of COASST, told Inside Climate News. “It’s like going from a Cliff bar to a rice cake. You can eat the same volume, but you’re not going to get the same nutrients. If you’re a predator, you have to work harder and spend more energy to get energy.”

The combination of the birds molting — a period when they need more energy — and the shortage of high-energy food supply, triggered by a warming ocean, may have caused the 2016 puffin mass die-off, the researchers conclude.

While losing a few thousand sea birds may not seem like a big deal, this mass die-off is part of a bigger ongoing decline, which is “almost certainly caused by ongoing climate change,” Tim Birkhead, emeritus professor of zoology at the University of Sheffield, wrote in The Conversation.

“We mustn’t get used to such events and we cannot afford to ignore the signs that climate change is not just continuing, but accelerating, and as that happens populations of seabirds (and many other forms of wildlife) will continue to decline,” he added. “We need to ensure we have robust monitoring systems in place to document these depressing changes in bird numbers, and we need to do everything we can to reduce the root cause: climate change.”

Citation:

Jones, T., Divine, L. M., Renner, H., Knowles, S., Lefebvre, K. A., Burgess, H. K., . . . Parrish, J. K. (2019). Unusual mortality of Tufted puffins (Fratercula cirrhata) in the eastern Bering Sea. Plos One, 14(5). doi:10.1371/journal.pone.0216532