Does Climate Change Starve Puffins?
Paul Kando
Tufted puffins up in the Bering Sea are dying, largely because of starvation and stress brought on by changing climate conditions, report researchers in the journal Plos One. The puffins' food supply has been disrupted by changes in air and sea temperature and diminishing winter ice levels, according to the new study.
photo credit: CraigTravel.com
Tufted puffins normally feed on krill and small fish, now in shorter supply and mostly consumed by bigger predators. Starvation is inevitable given how much food puffins need — normally about 30% to 50% of their body mass every day. That's a lot of food. If a puffin doesn't eat one day, it is in big trouble. If it doesn't get enough on four days, it dies.
In contrast, larger cold-blooded fish like cod normally eat only about 0.1% to 0.2% of their body weight each day. But when the water temperature increases, the metabolic rate of fish rises as well—by as much as 30% to 50%. This creates a bottleneck in the food chain where larger fish eat more of the smaller fish that puffins would normally prey on.
Increases in ocean temperatures have resulted in historically low sea ice extent on the Bering Sea over the last five years. When such changes occur, certain species lose out in the competition for food. Tufted puffins live and mate throughout British Columbia and Alaska, with big concentrations along the islands of the Bering and Chukchi Seas. Researchers examined more than 300 puffin carcasses found on the Bering Sea’s St. Paul Island, finding them extremely emaciated from apparent starvation and stress.
When a bird dies at sea, it floats on the surface for up to two weeks, pushed along by the wind. If after that time the corpse doesn't wash up on land, it will sink. Using wind data, researchers estimate the total number of dead puffins during a four-month research period to be between 3,150 and 8,500.
After breeding, puffins migrate somewhere with good access to food. They have to keep a little reserve through the migration because as soon as they get to their destination, they drop their flight feathers and become flightless for up to 40 days. They still have enough wing area to ”fly underwater” after their prey, but not as fast, so their ability to catch fish is impaired.
Like their Tufted cousins, Atlantic puffins — whose colorful beaks and penguin-like antics have made them a tourist draw from Maine to Iceland — have become a barometer of ecosystem health.
Puffins were virtually wiped out in Maine in the mid-19th century by fishermen who threw nets over puffin hideaways to catch them by the thousands. Restored to midcoast islands by scientists, puffins still have threatened status in Maine. And they were recently listed as endangered in Europe, where Icelanders caught and consumed them as a delicacy as recently as six years ago. Iceland’s big colonies – some 2.5 million breeding pairs – have been in decline because of shortages of forage fish.
Researchers have seen a correlation between warmer waters and food stress in puffin chicks worldwide. Off Maine’s coast, the birds were recovering nicely until recent years. Since 2004, however, the Gulf of Maine has warmed faster than anyplace else on the planet, except for an area northeast of Japan.
The warmest year on record for the Gulf of Maine was 2012, when surface temperatures reached 68.2 degrees, 5 degrees above normal, the warmest level ever recorded. That ocean heat wave disrupted the puffins’ food supplies — juvenile white hake, sand lance and herring — and only 15% of Maine’s puffin chicks survived.
2016 was the second-warmest on record, with average sea surface temperatures 3 degrees above normal. The warming has been more pronounced in the eastern half of the Gulf, with the western half remaining close to normal. This may account for the differing experiences of Maine’s puffin colonies. Machias Seal Island, out to the East and home of the largest puffin colony in the Gulf of Maine, had the worst breeding season ever recorded in 2016, with the vast majority of chicks starving to death in their burrows. That disaster followed a sudden drop in the puffins’ small-fish food supply. In coastal areas, on the other hand, where most people see these colorful birds, things remained close to normal.
More puffins will surely die, on both the Bering Sea and the Atlantic. Luckily, however — so far — the puffins do not appear headed for complete extinction.