Scientists have discovered that an annual event when Emperor penguins completely shed and regrow their feathers is putting the birds in peril as Antarctica is transformed by a warming world. Each year the birds must stay on platforms of floating ice for long enough to replace weather-beaten feathers with new, waterproof coats. But in 2022-24 Antarctic sea ice shrank significantly, largely down to climate change, depriving the birds of safe places to moult. Now scientists who track the animals using satellite pictures can no longer find most of the birds. They fear that thousands of penguins may have frozen in Antarctica's icy waters. "This was really an "oh my God" moment," says the scientist behind the findings, Dr Peter Fretwell at British Antarctic Survey, who has worked on Emperor penguins for 20 years. "You could see this was something game-changing for Emperor penguins. Suddenly you're thinking, well, have we got time to save them?" he says.…