Halley Bay has long been home to one of the largest emperor penguin colonies in Antarctica, second only to Coulman Island in the Ross Sea. Over the past 60 years that researchers have been observing the Halley Bay colony, between 14,300 and 23,000 pairs have flocked to the site’s sea ice to breed. But since 2016, breeding failures have been “catastrophic” and the penguins appear to have abandoned what was once a reliable haven, according to a new study published in Antarctic Science.
The trend was reported by Peter Fretwell and Philip Trathan of the British Antarctic Survey, who studied high-resolution satellite images of Halley Bay, looking for clues—like poop stains and shadows—that point to population size. The researchers think the trouble started in 2015, after the strongest El Niño in decades began disrupting Halley Bay’s “fast ice,” or sea ice that is anchored to the shore or ocean floor. Between April and December, the penguins depend on fast ice to provide stable ground for mating, incubating eggs and caring for chicks. But in 2016, reports the BBC’s Jonathan Amos, the ice broke apart before the baby penguins would have developed the feathers they needed to swim. Thousands of them appear to have drowned.
According to the British Antarctic Survey, the ice failed to properly reform in 2017 and 2018, leading to “the death of almost all the chicks at the site each season.” And now, the colony at Halley Bay has largely disappeared.
It seems that many of the adult emperor penguins have travelled elsewhere to find more reliable breeding ground. Satellite data shows that a colony of emperor penguins at the nearby Dawson-Lambton Glacier suddenly experienced a “massive increase” in numbers starting in 2016, the study authors write.
In some respects, this is good news. While the researchers don’t know if the breakup of ice at Halley Bay was caused by warming, previous research has found that emperor penguins are at risk of “losing 50 to 70 percent of their numbers before the end of this century as sea-ice conditions change as a result of climate change,” according to Trathan. Previously, it wasn’t clear how the penguins would respond to dramatic changes to their environment. The new study suggests that when faced with unstable breeding sites, the birds will move to more suitable grounds.
Still, there is reason to worry. For one, scientists had thought that the Weddell Sea, where Halley Bay is located, was thus far immune to the shifts in sea ice that have been observed elsewhere. The sea is, according to the Associated Press, one of the coldest regions of Antarctica. “I thought the Weddell Sea would be one of the last places we would see this,” Tranthan tells Erik Stokstad of Science. “The fact that these penguins are still vulnerable is a surprise.”
Additionally, as the study authors note, the Halley Bay colony comprised around 23 percent of the regional emperor penguin population, and it is “highly likely that the regional population in the Weddell Sea was impacted following the loss of at least three consecutive breeding seasons.” And while emperor penguins seem able to adapt to sea ice changes and severe breeding failures by seeking out better sites to raise chicks, there could come a point, as our world continues to warm, that they will run out of places to go.
“It could well be that in decades to come,” Fretwell tells the BBC’s Amos, “very few if any places will be viable for emperor penguins.”