Penguins are birds that live by the sea most of their lives. There are seventeen different species of penguins in the world. Although each of the species are slightly different, all of the adult penguins have black backs and white bellies. Like all birds, penguins have wings, a beak, and bodies covered in feathers. They also lay eggs.

Penguins are one of the birds that can't fly, although it looks like they're flying when they swim underwater. Penguins' wings are adapted for life in the water. They have become narrower, stiffer, and flatter than other bird wing, and wing feathers are short, so they are not well built for flying. Penguin's wings look more like flippers of the dolphin, and they help penguins move through the water just as a dolphins' flippers do. Emperor penguins are the largest species at over 3 feet tall (1 metre). The smallest species of penguins are fairy penguins, which only grow up to 16 inches (41 centimetres).

Penguins are some of most social birds in world. Although penguins spend some time alone, they spend much of their lives with other penguins of the same kind. Penguins form groups to swim and dive, to feed, to travel from one place to another, and also to breed. Chinstraps are the most common penguin species. They have white faces and a thin black stripe under their chin. They are about 28 inches (70 centimetres) tall.

A rookery of penguins is made up of lots of families. Each family consists of a male and female pair of adults and their baby penguins. Penguins gather in rookeries of different sizes. They gather in rookeries mainly to breed, but to also protect each other against enemies. The biggest rookeries number several million penguins, and the smallest rookeries only number a few hundred penguins. A rookery almost always contains penguins of only one species.

All seventeen species of penguins live in the southern hemisphere. Most penguins live on the coasts of Antarctica or on small islands nearby. Some penguins live in warmer places on the coast of South America, Africa, Australia, and New Zealand. However, even if penguins live in warmer places, they all need to live reasonably near cold, ocean currents because this is where they find prey. For most of the time, penguins are in the sea. Most species of penguins spend at least two-thirds of their lives in the water. Penguins are excellent swimmers. When penguins swim, they use their wings as flippers and their feet to steer. They have wide, flat feet that push them forward, and waterproof feathers that keep them dry. Penguins can swim in very cold water. Their dense feathers and thick layers of blubber under their skin keep them warm and cozy, even in the iciest ocean.

All penguins have white fronts, and black backs. They catch food in the ocean, so their colouring camouflages them. Penguins swim with their back turned up to the sky, and their belly facing the bottom of the ocean. If an enemy swims underneath a penguin and looks up, the penguin's white belly blends with bright sky above it. If an enemy flies above a penguin and looks down, the penguin's black back is hard to see against the dark water.

Penguins have a sharp beak that is short and thick, and they have a strong grip. They also have thousands of tiny feathers to keep them warm.

Emperor penguins can weigh as much as a 100 pounds, and are four feet tall. The fairy penguin is the smallest; it is only one foot tall.

Penguins mainly eat small fish, squid, and crabs. They catch and swallow food whole while they are swimming. Some species of penguins prefer specific types of food. For example, Ad�lie penguins eat mostly krill, which are small, shrimp-like animals. Penguins can swallow up to two pounds of krill a day. Different species of penguins travel different distances to find food. Ad�lie penguins feed together in shallow waters near the coast. Emperor penguins travel much farther away to look for prey in deep waters. King and emperor penguins may migrate over 1000 km to find large fish and squid.

Penguins feed mostly during the day. When they spot prey, they swim quickly after it. Penguins have good eyesight and can see better underwater then they can on land. Scientists think that some penguins manage to catch certain types of fish and squid at night because these animals glow in dark. Penguins catch their fish with a sharp beak that is short and thick, and has a strong grip. They also have mouths and tongues lined with little backward pointing spines to help hold on to slippery prey. Some, like emperor and king penguins, have beaks that curve downward. This helps them catch fast-moving fish and squid in deep waters.

Penguins need water to survive. To get water, penguins eat snow and drink fresh water and seawater. Too much salt water could harm bodies, so they get rid of it through a special gland in their beak. Many penguins hunt for food on their own, but close to other penguins. Some kinds of penguins work together to catch prey. Humboldt penguins hunt together for shoals of fish such as anchovies. When they spot a shoal, members of team bob their heads to give the signal to dive together. Then they dive towards fish from all directions at once, which forces the shoal to form a tight ball. This makes it easy for penguins to swim straight into the ball to feed. People have also seen emperor penguins work together in the same way. Parents take turns fetching food for their chicks. They carry fish back to chicks and feed their chicks. As their chicks get bigger, both of the parents have to go to sea at the same time to get enough food for them.

Penguins breed in rookeries. In a rookery, penguins lay eggs at roughly the same time so the young are roughly same age. Young penguins are called chicks. There are no trees or plants to make nests, so mothers lay the eggs on ice. The mother penguin passes the egg to its partner. The father penguin tucks it in a fold of skin above its feet. The father penguin's body and feathers on the egg will keep the egg warm.

Then the mother penguin goes to the ocean, many miles away. There it will find food. Few adults guard them from predators, while parents are away at sea finding them food. After two weeks, the egg starts to crack. The baby penguin pecks its way through the shell. When it's hatched, the chick stays on its father's feet to keep warm. It would quickly die if it fell on ice. Afterwards, the mother penguin returns.

She gives a special call, and its partner knows the call and answers back. She finds him among thousands of other penguins. The father penguin is hungry. He passes the chick to his partner, and this time he is going to go to the ocean.

The father penguin is thin and tired after taking care of the chick so long without eating. It's his turn to the leave rookery and find food. Back at the rookery, the mother feeds her chick. This time, the chick stays on its mother's feet. The chick has grown a lot by the time its father comes back. The chick passed to its father, who must get it onto his feet quickly, so it doesn't freeze. He will feed the chick for a while.

The chick is now seven weeks old, and too big to sit on its parent's feet. The mother and father still take turns bringing food from the ocean. The ice is beginning to melt, and the open water is closer to the rookery.

When chicks are five months old, they lose their fluffy grey feathers, and grow a coat of stiff black and white feathers, which are waterproof. By summer, the young penguins are old enough to look after themselves. Their parents leave them at the rookery to go to the feeding ground. They find plenty of food in the ocean.

By now, the young penguin needs to feed itself. There is no food at the rookery, so it must go to the ocean. With its new feathers, the young penguin is ready to go in the water. It can go as deep as 870 feet when it dives for food. Penguins can hold their breath and stay under water for long time. They chase fish and squid, and catch them with its sharp bill. At end of summer, they travel back to the rookery. They have molted and grown new feathers for the winter.

The only enemies penguins have are killer whales, leopard seals, and sea lions.