Penguins are flightless seabirds uniquely adapted to life in some of the harshest environments on Earth. Of the 18 recognised species, most live in the Southern Hemisphere, with the largest concentrations in Antarctica, South America, South Africa, and New Zealand. The emperor penguin (Aptenodytes forsteri) is the tallest and heaviest, standing up to 1.2 metres and weighing as much as 45 kilograms.
While penguins cannot fly, they are exceptional swimmers. Their wings have evolved into stiff, flipper-like appendages perfectly shaped for propulsion through water. Gentoo penguins — the fastest of all penguins — can swim at speeds of up to 36 km/h, using their feet and tail as a rudder. They can dive to depths of over 500 metres and hold their breath for more than 20 minutes.
Emperor penguins breed during the Antarctic winter, one of the most extreme parenting feats in the animal kingdom. After the female lays a single egg and departs to feed at sea, the male balances the egg on his feet beneath a warm brood pouch. He stands in blizzards that reach −60°C and winds of 200 km/h for up to 65 days without eating, losing nearly half his body weight before the egg hatches and the female returns.
Penguins are highly social birds, forming colonies — called rookeries — that can number in the hundreds of thousands. They communicate through a rich repertoire of calls; parent and chick can locate each other among thousands of identical-looking neighbours purely by voice. Climate change poses an increasing threat to penguin populations, particularly species that depend on sea ice for breeding and feeding.