Penguins (order Sphenisciformes, family Spheniscidae) are a group of aquatic, flightless birds . They live almost exclusively in the Southern Hemisphere, with only one species, the Galapagos penguin , found north of the equator. Highly adapted for life in the water , penguins have countershaded dark and white plumage, and their wings have evolved into flippers. Most penguins feed on krill, fish , squid and other forms of sea life caught while swimming underwater . They spend about half of their lives on land and half in the oceans .
Although almost all penguin species are native to the Southern Hemisphere, they are not found only in cold climates, such as Antarctica . In fact, only a few species of penguin live so far south. Several species are found in the temperate zone, and one species, the Galápagos penguin , lives near the equator.
The largest living species is the emperor penguin (Aptenodytes forsteri): on average , adults are about 1.1 m (3 ft 7 in) tall and weigh 35 kg (77 lb). The smallest penguin species is the little blue penguin (Eudyptula minor), also known as the fairy penguin , which stands around 40 cm (16 in) tall and weighs 1 kg (2.2 lb).