Birds

Birds are animals with feathers.
There are many different kinds of bird.
Birds live in most places in the world.
They have two legs and a beak.
Most birds fly but some do not.

Animals
Birds are part of the animal kingdom and are found everywhere on earth, in most habitats, including the Arctic and Antarctic.

They are warm-blooded, which means they can keep a warm body temperature constantly, even if their surroundings are cold.

There are about 10,000 different species (kinds) of birds. They are grouped into about 150 families.

In Australia there are 770 species of native birds, and in addition there are introduced species such as sparrows and Indian mynahs.

Bones
Birds are vertebrates, meaning they have a backbone. Some bones in a bird's skeleton are fused, or joined, so that they are like one bone. This makes the skeleton stronger for flying. A bird's bones are hollow but strong, which makes the bodies of flying birds light in comparison to size.

Heart and Lungs
Birds use a lot of oxygen, especially when they fly. For that reason, birds have a strong circulatory system with a powerful heart that beats more frequently than human hearts do. Birds breathe differently from other animals with lungs. Their lungs are quite small and tube-like, but air sacs keep the lungs permanently inflated even when the bird is breathing out. Air flows first to the air sacs, which send oxygen-filled air into the lungs. This provides birds with plenty of oxygen.

Diet
Birds use a great deal of energy, especially when they are flying. They need to eat a lot in order to keep up that energy . They spend a great deal of their time looking for food. Some birds are carnivores, or meat eaters. Eagles and other birds of prey like falcons, hawks and kites, are carnivores. Penguins, pelicans and waterbirds are carnivorous because they eat fish. Some birds are herbivores, and eat plants or parts of plants, such as seeds, nectar and fruit. Parrots, honeyeaters and finches are herbivores. Some birds, such as emus and starlings, are omnivores because they eat plants and meat.

Depending on their diet, birds play an important part in the environment. Carnivorous birds like eagles and falcons clean up the carcasses of animals that have died or have been killed on the roads. Other birds help keep insects under control, spread seeds or take pollen from flower to flower. The Rainbow Lorikeet has a brush-tipped tongue to help collect and spread pollen from the flowers it feeds on.

Birds have excellent eyesight, and this helps them find food. The shape of their beaks helps them in catching and eating their food, and there is a huge variety of beak shapes among birds. For example, the hooked beak of an eagle helps it tear meat from bones, while the differently hooked beak of a parrot helps it open up a seed covering to eat the seed inside. Honey eaters have long thin beaks that fit inside a flower to reach the

nectar. Some honey eaters have beaks designed to fit specific flowers that no other nectar eater can reach. Some wading birds have long sharp beaks that reach down into the water to stab a fish. Pelicans have a whole fishing basket attached to their lower beak. Beaks are also used for defence, gathering materials for nests, nest building, cleaning feathers and courting.

Birds do not have teeth, although their ancestors did. The food they eat goes into a part called a crop, where it is stored until it travels to the gizzard. In the gizzard, which is made of muscle, small stones and grit grind up the food. A bird's tongue has a bone inside it. Tongues help a bird drink, and to hold and tear food.

Movement
All birds have wings, but not all birds fly. Most birds can fly. Some birds run fast. Some birds swim well, on or under the water. Many birds can do various combinations of these. To assist with flying, there are 2 main flight muscles on each wing, and 48 other muscles within the wings and shoulders.

photograph © [2008] Jupiterimages Corporation

Flying

Most birds fly. The shape of their wings helps fly. Many fly long distances, or fly incredibly fast. There are 2 muscles on each wing and 48 other muscles in the wing and shoulder area to help birds fly.

Example

The albatross flies huge distances, and rarely comes to land.

Running

There are some birds that cannot fly, including the emu and ostrich.They have developed long legs, and they run very fast. There are other birds that can fly small distances, but prefer to walk or run. Wing bones are smaller in flightless birds, and they don't have the keel bone in the chest for flight muscles to attach to.

Example:

The ostrich is the fastest two-legged runner, and the largest of all the birds. The kakapo is a flightless parrot found in New Zealand.

Swimming

Some birds swim on the water, such as swans, ducks and geese. Some water birds, such as cormorants, are able to dive into the water to catch fish under water. These birds also fly, and walk or run on the land. Other birds, such as penguins, swim under water, holding their breath for long periods of time. Penguins have small wings and don't have a keel bone in the chest for flight muscles to attach to.

Example:

Swimming penguins look like they are flying under the water. When they are on land, penguins walk awkwardly.