Birds are animal with feathers. Because they can fly, they are the fastest animals on Earth. Some birds can reach speeds of up to 160km an hour. However, not all birds can fly. Some birds, like ostriches can run and penguins can swim.
There are about 10,000 kinds of birds. The smallest bird is the hummingbird which gets only about 5cm big and the largest one is the ostrich which may grow up to 2.5 metres tall. Birds live everywhere in the world—from the cold polar regions to the rain forests of Africa.
There are birds, like ducks or seagulls that always live near water. Many birds from colder areas migrate to warmer regions to avoid harsh winters, but others stay in their living area all through the year.
All birds hatch from eggs. Female birds lay their eggs in nests that they build. Baby birds remain in the nest for several weeks or months after hatching. Their parents feed them and care for them until they are old enough to leave them.
Birds belong to the group of animals that have backbones, like we do. These animals are called vertebrates. Like mammals, birds are warm-blooded – their temperature always stays the same, even if it is cold outside. Birds don't have teeth, they have a hard beak that they use to get food or defend themselves.
A bird has a light but strong skeleton and bones that are hollow. Many of them are joined together. The strongest muscles are in the wings. These powerful wings help birds stay in the air. Some birds, which are fast runners or have a lot of weight to carry, have the strongest muscles in their legs.
Feathers cover most of a bird's body. Some birds have up to 25,000 feathers. In many types of birds the feathers are brightly coloured in order to attract other birds. Birds lose their feathers at least once a year. They grow new ones – mostly during the breeding season.
The bills or beaks of birds are built differently, depending on what they eat. Woodpeckers have a chisel-like bill, so they can bore into trees and look for insects. Ducks have flat bills because they eat plants that float in the water.
All birds have two legs; however, they don't always look the same. Birds that fly most of the time have very short legs and wading birds or fast runners have long ones. The majority of birds have 4 toes on each foot – one of them points backwards. Climbing birds have two toes pointed to the back to give it more grip.
Birds that mostly live in the water have skin between their toes. This lets them swim better than others.
In order to fly, birds need a lot of oxygen, so they need a powerful heart to get it into their lungs. A bird's heart beats much faster than ours does – up to 1000 times a minute.
Birds have a good sense of sight. In proportion to other animals, they have the biggest eyes. They are on the sides of their heads, so each eye can see in a different direction. This is called monocular vision.
Birds have ears, but they are not visible. In most cases, they are covered with feathers. They hear as well as we do, some of them even better. Some birds use their sense of hearing to navigate in dark caves where they can't see anything.
Birds' sense of smell is not very well developed, but there are some birds that are almost blind and rely on their smell to get food.
A bird's wing is curved on the top and flat on the bottom. The air can flow faster over the top than under the bottom part. Fast moving air has less pressure than slow-moving air, so the air under the wing pushes it upwards. This is called lift. To climb very high, birds start flapping their wings and push more and more air down.
Some birds can fly really fast. Falcons are considered to be the fastest birds. Experts think they can travel at speeds of up to 250km/h.
Birds are the only animals with feathers. They weigh very little, but birds could not live without them. They help them fly, keep them warm and keep rain and snow away from their skin.
A feather is made up of a central shaft that is very stiff. The vanes on both sides are made up of thousands of tiny barbs.
We need birds for many reasons. In nature, birds eat fruit and carry the seeds from flower to flower. Some birds, like chickens and ducks provide us with meat or eggs. Others help farmers eat insects that attack their fields.
But some birds are thought to be more dangerous than helpful. Starlings and pigeons have become numerous in cities and make lots of dirt.
People have always hunted birds for food. Turkeys or ducks are hunted because of their valuable meet. Farmers today produce hundreds of millions of chickens every year for meat.
Birds can also be kept as pets. Parrots and canaries are very common pets because they can be trained to talk or to whistle.
Birds migrate to certain places in order to get food and water all year round. They also travel to other places to escape from extreme weather and temperatures. Seabirds are the greatest travellers. Some of them travel over a distance of 30,000km or more every year.
Migrating birds have many ways of finding out the right direction. They help themselves by using the position of the sun or moon during the daytime and watch the stars at night. Some of them get help from familiar things they see or hear.
Sometimes, birds get lost and fly in wrong directions. They are observed thousands of km away from their normal living areas.