Thanks to the cool waters of the Humbolt Current, one species, the Galapagos penguin, lives on the equator. In size they range from the gigantic emperor penguin, standing about 40 inches high, and weighing up to 90 pounds, to the diminutive fairy penguin of the Australian region that attains a length of just over a foot. While there is a considerable variation in the body markings from species to species, in general the pattern calls for a white breast and dark back. Indeed, it has been said that if the heads were removed it would be difficult to distinguish between any of a dozen species. Head markings are strongly characteristic, however, and here some species exhibit yellow and orange that may extend to the upper breast, or streaks and rings of white, or tufts of feathers.
Penguins are gregarious in the extreme.
The nesting rookeries often contain thousands of birds. Some species, such as the emperor and king penguins, make no formal nest, but incubate the single egg by holding it on the feet for the entire period of incubation, which, in the king, is known to last about 52 days. During this period the male and female take turns holding the egg, relieving each other at intervals which, in the Edinburgh Zoo, where several king penguins have hatched, ranged from half a day to more than a week. Other species make crude nests that may be anything from a shallow depression in the soil, or a burrow, to a jumble of rocks. Until then they are fed by their parents, by regurgitation.