Adélie penguins have had a rough time on the western side of the Antarctic Peninsula, where warming linked to climate change has occurred faster than almost anywhere else on the planet. This and other factors have led to a sharp decline in Adélie’s population numbers in recent decades.
But on the east side, it’s a different story.
Lynch, a Stony Brook University statistical ecologist who studies penguin populations and how they change, “It’s just a whole train wreck on the western side of the peninsula.” “But on the east side, the population is stable and in good health.”
used dr. Lynch has satellite imagery in a lot of her work, but He also organizes penguin survey expeditions to the peninsula, the northern part of Antarctica. Last time, in January, three of her current and former students did their Ph.D., on the islands on the eastern side of the peninsula in the Weddell Sea.
Their work showed that the population of Adélie there had not changed much since previous censuses that had been taken over the past two decades. This suggests that as global warming continues and Adélie populations decline in other parts of the continent, Weddell may remain an important sanctuary for birds.
“It’s a good confirmation that where the climate hasn’t changed drastically, population hasn’t changed drastically,” said Dr. Lynch.
The Weddell Sea is known to be ice, which is a function of the rotating current, or rotation, that keeps much of the ice pack inside the sea for years. The ice makes it difficult for most ships to sail. (The Weddell is where explorer Ernest Shackleton’s Endurance ship crashed in ice a century ago. Its wreck was found last month.)
Over the years, Dr. Lynch’s students have conducted surveys of penguins from “ships of opportunity,” often sailing on cruise ships in exchange for lecturing or otherwise providing assistance. On the Antarctic Peninsula, these ships usually remain on the western side, and regulations limit shore visits to a certain set of colonies.
It was January’s voyage on the Greenpeace ship that he ventured around the tip of the peninsula northwest of Weddell. “It’s a place we wanted to get to,” Dr. Lynch said. “A lot of these colonies haven’t been visited in a very long time, if ever.”
The three researchers – Michael Withington, Claire Flynn and Alex Borovich – used drones and manual counting to determine the number of chicks in colonies on Joinville, Vortex, Deville and other islands.
Ms. Flynn, a first-year doctoral student at Stony Brook University, said manual counting takes time. Counters mark a specific area within a colony – perhaps a group of nests, or an area marked with bird walking paths – and count all the chicks inside three times to ensure accuracy. At Penguin Point, a particularly sprawling colony on Seymour Island that houses 21,500 chicks, the count took two days. (Adélies usually produce two chicks per breeding pair each year.)
“It got really boring, we went back to them three times,” Flynn said. “But this is a really cool place, and a great job to do.” Birds can be entertaining, she said, such as when a hungry chick viciously chases after a parent who is asking for food.
Adélies are among the most numerous penguin species 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 make nests on dry ground. Chicks hatch around November, in the late southern hemisphere spring, and the parents take turns guarding them and foraging for food that they vomit for their offspring. Antarctic Adélies choose their diet: they eat only krill, which are small crustaceans, although in other places they also eat fish.
Krill and ice, or the lack of both, are the root cause of the problems of the Adélies on the western side of the peninsula, which were warming in part as a result of atmospheric circulation patterns that arose in the warm tropics. Krill thrive in cold, icy conditions, as warming has reduced sea ice, and krill has become less abundant as well.
This leaves Adélies without enough food that they need for themselves and their chicks. “The fact that they are eclectic eaters on the peninsula is detrimental to them, as it is very much related to the health of the krill population,” said Dr. Lynch.
Populations have fallen by as much as 90 percent in some parts of the West Side, and Gentoo penguins, recognizable by their bright orange beaks, have largely taken hold. “They will eat anything, and they will breed anywhere,” Dr. Lynch said of Gentos. “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 become unfavorable for the Adélies.
Weddell has also been proposed as a marine protected area under the Antarctic Treaty, which would further protect the penguins and other life there, from human activities such as krill hunting, especially as the ice cover has decreased due to warming and the area has become more accessible. “As scientists, we want to locate all the important biology” of the effort, said Dr. Lynch.
The finding that the population is stable “does not mean that climate change is not happening in the Weddell Sea,” she said. “It just means that by virtue of oceanography it stays cold and icy which is exactly the kind of place these Adelies need to live.”