Penguins: Sphenisciformes

Penguins have large heads and long bodies. They resemble humans when they waddle around on their two webbed feet. Their short feathers, which provide excellent insulation against the cold water and air temperatures, are black on their backs and white on their chests, giving the appearance of a tuxedo. Their wings are stiff flippers that help them navigate the ocean waters.

Species vary in size, so penguins can weigh less than 3 pounds (1.1 kilograms) or as much as 88 pounds (40 kilograms). They can stand less than 18 inches (45 centimeters) high, or almost 4 feet (115 centimeters) tall. Males are somewhat bigger than females, but look similar otherwise.

Penguins cannot fly and their bones are much more solid and heavy than those of most birds. This is an adaptation that allows them to dive for food. Penguins differ from other birds in that, except for a patch on their bellies, their entire bodies are covered with feathers. Birds usually have feathers growing only in certain sections of skin.