They make their nests in enormous gatherings called colonies. Most colonies occur on islands. Some lie in coastal areas, but only where there are no land mammals that might eat the penguin chicks or eggs. A penguin colony can have thousands of members. The colonies are noisy because the birds often call to one another with a braying sound like donkeys.
Penguins recognize each other mostly by their voice.
Most penguins make their nests by digging shallow burrows under large rocks or bushes. Antarctic penguins build nests of pebbles on the ground because the frozen earth is too difficult to dig. The king penguin and emperor penguin build no nests at all. They keep their eggs or small chicks warm under a fold of their belly, holding them on the tops of their feet. A pair of male and female penguins may nest together every year for many years.