Penguin Penguin 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 which they catch while swimming underwater. They spend roughly half of their lives on land and the other half in the sea. Although almost all penguin species are native to the Southern Hemisphere,
Ratite as a whole probably had an origin in the northern hemisphere. Early Cenozoic northern hemisphere paleognaths such as "Lithornis", "Pseudocrypturus", "Paracathartes" and "Palaeotis" appear to be the most basal members of the clade. The various ratite lineages were probably descended from flying ancestors that colonised the south in multiple waves, probably initially in South America, and then evolved gigantism. Loss of flight allows birds to eliminate the energetic cost of maintaining flight-enabling pectoral muscle mass. The basal metabolic rate of volant species is much higher than that of flightless terrestrial birds. But energetic efficiency can only help explain the loss