Penguin Keyring. Penguins are a group of aquatic, flightless birds living in the Southern Hemisphere. The largest living species is the Emperor Penguin, adults average about 1.1 m tall and weigh 35 kg. Some prehistoric species attained enormous sizes, becoming as tall or as heavy as an adult human! Most penguins feed on fish, squid, and other of sealife caught underwater. They spend half of their life on land and half in the oceans. Penguins seem to have no special fear of humans and have approached explorers without hesitation.