Sphenisciformes

Sphenisciformes is the order of birds that includes penguins. All living penguin species inhabit the Southern Hemisphere, with the greatest diversity in the subantarctic regions surrounding Antarctica and along southern coasts of South America, Africa, Australia, and New Zealand; one notable exception is the Galápagos penguin, which lives near the equator. Penguins spend most of their lives at sea and come ashore primarily to breed.

Penguins are flightless and highly specialized for an aquatic lifestyle. Their bodies are streamlined for swimming, with dense plumage and a layer of blubber for insulation. The wings have evolved into rigid flippers used to propel them underwater, while their legs and feet are adapted for steering and propulsion on land and ice. They possess salt glands above the eyes to excrete excess seawater. Penguins are strong divers, capable of reaching substantial depths in pursuit of fish, squid, and crustaceans.

Taxonomy and evolution: Sphenisciformes comprises one living family, Spheniscidae, containing several genera that include Aptenodytes (emperor and king penguins), Pygoscelis (Adélie, chinstrap, Gentoo), Spheniscus (African, Magellanic, Humboldt, Galápagos), Eudyptula (little penguin), Megadyptes (yellow-eyed penguin), Daption (Cape penguin), and Eudyptes (crested penguins). The group encompasses around 18 extant species. The fossil record indicates penguins originated in the Late Cretaceous to early Paleogene and subsequently adapted to a fully aquatic, flightless existence.

Ecology and conservation: Penguins feed mainly on fish, squid, and krill, captured during deep and extended dives. They breed in colonies, with parental duties shared in many species. Several penguin species face conservation challenges from climate change, overfishing, introduced predators on breeding grounds, and habitat disturbance; some are listed as threatened or vulnerable.