Penguins are flightless, aquatic birds that, outside of zoos, live exclusively in the southern hemisphere. All species are black and white, are very social, and divide their time fairly equally between land and water.
As of 2015 there are as many as 20 known species of this bird, the largest being the emperor penguin at nearly 4 feet tall. The smallest species is the little blue, who measures about 16 inches. The macaroni penguin is the most populous with over 11 million pairs. The gentoo penguin is able to swim up to 22 miles per hour.
Common knowledge suggests that penguins in the wild inhabit only extremely cold climates, but there are species living on every continent of the southern hemisphere. Larger species tend to live in very cold climates, and smaller varieties live in warmer areas. The penguins closer to the equator eat mostly fish. Closer to Antarctica the diet is predominately squid and krill. All of the penguin's hunting happens in the water.
Penguins nest, eat and swim in large groups. Mating often occurs in large groups, as well. Called rookeries, these groups sometimes number in the thousands. Mates find each other and their young among the crowd with the help of distinct calls.