Which flightless bird lives in Antarctica?

Penguins are the flightless birds of the far south, and Antarctica and its surrounding waters are home to species including the emperor and the Adelie. Their ancestors could fly, and the wings have since been reshaped into stiff, narrow flippers driven by heavy chest muscles, so a penguin genuinely flies underwater, using the same up-and-down wing stroke as a flying bird but in a far denser medium. That reshaping traded away flight entirely, which is only affordable because there are no land predators on the Antarctic continent to escape from. The rest of the anatomy follows the same cold-water logic: dense bones rather than the hollow ones flight requires, a thick layer of fat, and overlapping feathers packed tighter than in almost any other bird, with an air layer trapped underneath for insulation. Emperor penguins breed through the Antarctic winter, the males incubating a single egg on their feet while huddling.

No penguin species lives naturally in the Arctic; the whole family is confined to the southern hemisphere.