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