Adélie penguins have had a hard time on the western side of the Antarctic Peninsula, where warming related to climate change happened faster than almost anywhere else on the planet. That and other factors have caused Adélie’s population to plummet in recent decades.
But in the east, it’s a different story.
“It’s just a complete wreck just west of the ocean,” said Heather J. Lynch, a statistical ecologist at Stony Brook University who studies penguin populations and how they’re changing. Peninsula. “But in the east, the populations are stable and fairly healthy.”
Dr. Lynch uses satellite imagery in much of his work, but also organizes penguin expeditions to the peninsula, the northernmost part of the Antarctic continent. Most recently, in January, three of her current and former PhD students performed the count, on islands on the eastern side of the peninsula in the Weddell Sea.
Their research shows that the population of Adélie there has changed little from previous counts over the past two decades. That suggests that as global warming continues and Adélie populations decline in other parts of the continent, Weddell may remain an important bird sanctuary.
“It’s a great confirmation that in places where the climate doesn’t change so dramatically, populations don’t change significantly,” said Dr. Lynch.
The Weddell Sea is notoriously icy, a function of rotating currents, or gyroscopes, which keep most of the ice frozen in the sea for many years. Ice makes it difficult for most ships to navigate. (Weddell is where explorer Ernest Shackleton’s ship Endurance was crushed by ice a century ago. The wreck was found last month.)
For years, Dr. Lynch’s students have been conducting surveys of penguins from “ships of opportunity,” often traveling on cruise ships in exchange for teaching and help. On the Antarctic Peninsula, those ships often stayed west, and regulations limited shore visits to specific colonies.
The January voyage on a Greenpeace ship ventured around the tip of the peninsula into Northwest Weddell. “It was somewhere we wanted to go,” Dr. Lynch said. “A lot of these colonies haven’t been visited in a very long time, if ever.”
Three researchers – Michael Wethington, Clare Flynn and Alex Borowicz – used drones and hand counting to determine the number of chicks at colonies on Joinville, Vortex, Devil and other islands.
Ms. Flynn, a first-year doctoral student at Stony Brook, says counting hands takes a long time. The counter identifies a specific area within a flock – be it a group of nests or an area delimited by a birdwalk – and counts all chicks in it three times to ensure accuracy . At Penguin Point, a particularly large population on Seymour Island, home to 21,500 chicks, the count took two days. (Adélies usually give birth to two chicks per breeding pair each year.)
“It’s tedious, counting them over and over again,” said Mrs. Flynn. “But it’s just a great place to be and a great job to do.” And the birds can be entertained, she says, like when an angry hungry chick chases its parent demanding food.
Adélies are among the most numerous species of penguins found in Antarctica, with an estimated 3.8 million breeding pairs in colonies across the continent. They use their beaks to collect small stones to nest in arid land. The chicks hatch around November, in the late Southern Hemisphere spring, and the parents take turns guarding them and foraging for the food they vomit for their chicks. The Antarctic Peninsula Adélies are very picky about their diet: They eat only krill, a small crustacean, although elsewhere they also eat fish.
Krill and ice, or the lack of both, are at the root of the problems of the Adélies on the western side of the peninsula, which are warming in part because of atmospheric circulation patterns originating in the warming tropics. Krill thrive in cold, icy conditions, so as warming has reduced sea ice, krill has also become less abundant.
That leaves Adélies without enough food for herself and her chicks. “The fact that they are such picky eaters on the peninsula is bad for them, because they have so much to do with the health of the krill population,” said Dr. Lynch.
Populations have dropped by as much as 90% in some western areas, and Gentoo penguins, distinguished by their bright orange beaks, have made up the majority. “They will eat anything, they will spawn anywhere,” Dr. Lynch said of Gentoos. “I think of them as the urban pests of the peninsula.”
As the world continues to warm, models suggest that Weddell, and the Ross Sea in West Antarctica, will be the last places to turn unfavorable for the Adélies.
Weddell has also been proposed as a marine reserve under the Antarctic Treaty, which would further protect the penguins, and other creatures there, from human activities such as krill fishing, particularly as the ice cover decreases due to warming and the area becomes more accessible. “As scientists, we wanted to map out the location of all the important biology,” said Dr. Lynch.
Finding that the population is stable “doesn’t mean climate change isn’t happening in the Weddell Sea,” she said. “It just means that thanks to oceanography, it’s still cold and icy and exactly where these Adélies needed to live.”
