Adelia penguins have moved to the western part of the Antarctic Peninsula, where global warming has occurred faster than almost anywhere else on the planet. This and other factors have led to a sharp decline in the population of Adélie in recent decades.
But in the east, the story is different.
“It’s just a complete train wreck on the west side of the peninsula,” said Heather J. Lynch, a statistical ecologist at Stony Brook University who studies penguin populations and how they are changing. “But on the east side, the populations are stable and quite healthy.”
Dra. Lynch uses satellite imagery for much of his work, however also organizes penguin exploration expeditions to the peninsula, the northernmost part of the Antarctic continent. The last, in January, three of his current and former doctoral students did the count, on the islands of the eastern part of the peninsula in the Weddell Sea.
Her work has shown that Adélie’s populations there have changed little since previous counts over the past two decades. This suggests that as global warming continues and Adélia populations decline in other parts of the continent, the Weddell may remain an important bird sanctuary.
“It’s a good confirmation that where the climate hasn’t changed so drastically, populations haven’t changed dramatically,” Dr. Lynch.
The Weddell Sea is notoriously icy, a function of a rotating current, or turn, that keeps much of the ice floe in the sea for years. Ice makes it difficult for most boats to navigate. (The Weddell is where the Endurance ship of explorer Ernest Shackleton was crushed by ice a century ago. The wreck was found last month.)
Over the years, Dr. Lynch have conducted surveys of penguins from “ships of opportunity,” often sailing on cruise ships in exchange for lecturing and otherwise assisting. On the Antarctic Peninsula, these ships usually remain on the west side, and regulations limit visits to the coast to a specific set of colonies.
The January voyage was aboard a Greenpeace ship that ventured along the tip of the peninsula to the northwest of Weddell. “It’s a place we wanted to get to,” Dr. Lynch said. “Many of these colonies had not been visited for a long time, if not ever.”
The three researchers, Michael Wethington, Clare Flynn and Alex Borowicz, used drones and manual counting to determine the number of chicks in the Joinville, Vortex, Devil and other islands colonies.
The hands-on count takes time, said Ms. Flynn, a freshman at Stony Brook. The counters identify a specific area within a colony (perhaps a grouping of nests or an area bounded by bird paths) and count all the chicks inside three times to ensure accuracy. At Penguin Point, a particularly large colony on Seymour Island with 21,500 chicks, the count lasted two days. (Adélies usually produce two chicks per breeding pair each year.)
“It gets tedious to count them three times,” Ms. Flynn said. “But it’s an amazing place to be and such an amazing job to do.” And birds can be entertained, he said, like when a hungry chick furiously chases a father begging for food.
Adelias are among the most abundant penguin species found in Antarctica, with about 3.8 million breeding pairs in colonies across the continent. They use their beaks to collect small stones to make nests in dry land. The chicks hatch around November, in the late spring of the southern hemisphere, and the parents return to protect them and look for food that is regurgitating for their offspring. The Adélies of the Antarctic Peninsula are demanding with their diet: they only eat krill, a small crustacean, although in other places they also eat fish.
Krill and ice, or the lack of both, are the root of Adélies’ problems on the western side of the peninsula, which has been warming in part as a result of atmospheric circulation patterns originating in the tropics. they warmed up. Krill blooms in cold, icy conditions, so as warming has reduced sea ice, krill have also become less abundant.
This leaves Adélies without enough of the food they need for them and their chicks. “The fact that they are so demanding on the peninsula is detrimental to them, because they are closely tied to the health of the krill population,” Dr. Lynch said.
Populations have declined by as much as 90 percent in some parts of the western side, and Gentoo penguins, which are distinguished by their bright orange beaks, have largely taken over. “They’ll eat anything, they’ll breed anywhere,” Dr. Lynch said of Gentoos. “I think of them as the urban plagues 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 be unfavorable for Adélies.
The Weddell has also been proposed as a marine protected area under the Antarctic Treaty, which would further protect penguins and other life forms there from human activities such as krill fishing, especially as the deck of ice decreases due to warming and the area becomes more accessible. “As scientists, we want to chart where all the important biology is located” for this effort, Dr. Lynch said.
The finding that populations are stable “does not mean that climate change is not happening in the Weddell Sea,” he said. “It just means that by virtue of the oceanography, it’s still cold and icy and exactly the kind of place these Adélies need to live.”