Previously unknown colonies of emperor penguins have been spotted in new satellite imagery.

Emperor penguins, considered “near threatened” with extinction, are the world’s largest penguins. They raise their chicks in Antarctic winter on patches of frozen sea ice. But if the ice breaks up before the chicks have fledged, most will die.

At least some emperor penguins are moving their colonies as melting ice from climate change threatens breeding grounds, according to research released on Wednesday.

One penguin colony near Halley Bay appears to have moved around 30 kilometers (19 miles) to the east, said Peter Fretwell, a researcher at the British Antarctic Survey. He said unstable conditions beginning in 2016 had made the old location perilous.