The Antarctic’s second-largest colony of emperor penguins collapsed in 2016, with more than 10,000 chicks lost, and the population has not recovered, according to a new study.

Many of the adults relocated nearby, satellite imagery shows, but the fact that emperor penguins are vulnerable in what had been considered the safest part of their range raises serious long-term concerns, said Phil Trathan, the paper’s co-author and head of conservation biology with the British Antarctic Survey in Cambridge, England.

“That means that these places aren’t as safe as we thought previously,” Dr. Trathan said.

The colony at Halley Bay has all but disappeared, the research team at the British Antarctic Survey said in a statement.

Emperor penguins — the world’s largest — breed and molt on sea ice, chunks of frozen seawater. Awkward on land, they cannot climb icy cliffs and so are vulnerable to warming weather and high winds whipping across the ice. Under the influence of the strongest El Niño in 60 years, September 2015 was a particularly stormy month in the area of Halley Bay in Antarctica, with heavy winds and record-low sea ice.