Penguins are thought to have evolved from flying birds some 50 million years ago. Today, their wings are more like flippers and their stubby tails like a rudder. A layer of body fat helps the penguin store energy and provides additional insulation. Females usually lay one to two eggs during the brief Antarctic summer. Penguins breed in large colonies, or rookeries.
Nests are simple, usually made from stones and other debris washed in from the ocean.
The male and female share responsibility for incubating the eggs and feeding chicks. To protect the young from predatory birds and the frigid environment, one parent will stay with the chick for its first three to four weeks. Meanwhile, the second parent will hunt in the ocean for food. When the chick is approximately a month old both parents will go hunting, leaving the chick with its peers in a so-called nursery. Penguins feed on a variety of fish, squid, and krill.