Why fly when you can slide? Happy World Penguin Day! There are 18 species of these flightless birds, 17 of which live in the Southern Hemisphere. Today's Antarctic image stars Adélie penguins, discovered in 1840 by French adventurer Jules Dumont d'Urville, who named them after his wife, Adèle. Despite their small size, Adélie penguins are sleek swimmers and can dive as deep as 575 feet in search of shrimp-like krill or fish. They are social animals that gather in small colonies for foraging, hunting, and protection. While it may seem mischievous, Adélies steal pebbles from nearby nests to strengthen their own, safeguarding their eggs and chicks from Antarctica's harsh conditions and predators.