Bird

From Wikipedia, a free encyclopedia written in simple English for easy reading.

Example of a bird

Birds are a group of vertebrate animals. They form the class Aves.

They are warm-blooded and they lay eggs. They have feathers all over them, and they have wings. Their bones are hollow (with no bone in the centre). This allows many of them to fly. They usually have two legs with scales (flat, hard pieces of skin). People know of about 9000 different species (kinds) of birds.

1 Introduction
2 How birds have chicks
3 How the first birds were born
4 Birds and people
5 External links

[edit] Introduction

This is an ostrich, the biggest kind of bird

This is a hummingbird. Another kind of this bird, the Bee Hummingbird, is the smallest bird in the world

There are many sizes of birds. Some species are very small, for example hummingbirds, and some are very big, for example ostriches.

Most birds can fly. However, a few species of birds cannot fly. Penguins, ostriches, and kiwis are among them. Many birds of this kind never needed to fly, because they lived on islands, where no other animals hunted them. Then they were no longer able to fly. The birds started to have problems when people first came to their countries. It was easy to hunt the birds. People brought new animals, which could also eat these birds or their eggs. Several bird species that couldn't fly, disappeared completely when they all died after the fast changes. The most famous of these species are Dodo, Great Auk, and the moas.

Different kinds of birds eat different kinds of things. Some foods they eat include nectar (the juice in flowers), seeds, insects, rodents (e.g. rats), fish, dead animals, and other birds. Most birds are awake in the day. But some, like owls, are nocturnal (awake at night). Many kinds of birds travel a long way for food. They go to places that can only support them for part of the year. For instance, the Arctic Tern travels between the Arctic and Antarctica every year. Other kinds of birds, like the Wandering Albatross, spend all their time at sea.

There are many things most birds have. Most birds can fly with their feathered wings. They have a bony beak, with no teeth. They lay eggs with hard shells. They have a high metabolism, which means they use a lot of energy. Their skeleton is light and strong. Scientists have studied birds more than many other sorts of animals. There are hundreds of academic journals about birds.

[edit] How birds have chicks

Most male (father) birds have no sex organs we can see. But the male has two testes. In the breeding season, when birds find a partner, the male bird's testes grow hundreds of times bigger. The female (mother) bird's ovaries (the place where the eggs come from) also grow larger, but only the left ovary is active. The males of some kinds of birds have a phallus (penis), for example, birds which live on the water, ostriches and turkeys; but some kinds of birds have none. Male birds with no phallus keep sperm (seed) in their cloaca (the exit hole for most body fluids), and give it to the female when they press their cloacas together.

After the chicks (baby birds) come out of the eggs, the mother and father birds help their babies in different ways. Some baby birds can live alone after they are born (precocial birds); and some baby birds can not live alone (altricial birds). Many birds in nests on the ground can run very soon after they are born (nidifugous birds).

Some birds, for example pigeons, geese, and Japanese cranes, are "married" for life. The male and female live together all their life, or for a long time after having babies. Sometimes they have babies together regularly.

[edit] How the first birds were born

Many scientists think that birds are from the theropod dinosaur family. Specifically, birds are placed in the Maniraptora group of theropods. It is difficult to say if, when, or how they changed from dinosaurs into birds. Many small theropod dinosaurs seem to have had feathers; this was realized when people found their bones in Northeast China (Liaoning Province). The dromaeosaur they found, Cryptovolans, could probably fly well by moving its wings. Perhaps it was better at flying than Archaeopteryx.

The ancient bird Archaeopteryx was from the Jurassic time of pre-human history. It is famous, because it was one of the first things people found after Charles Darwin wrote his ideas about evolution in the 19th century. Today it is the oldest, simplest bird we know. Other early birds now dead are, for example, the Confuciusornithidae, Enantiornithes, Ichthyornis, and Hesperornithiformes.

[edit] Birds and people

Birds are an important thing for people to eat. The sort people eat most often most is the chicken and its eggs, but people often also eat geese, pheasants, turkeys and ducks. Other birds we sometimes eat are emus, ostriches, pigeons, grouse, quails, doves, woodcocks, songbirds and others.

At one time swans and flamingos were special food for the rich and powerful, like some Emperors of Rome, but people are usually not allowed to eat them now.

Many species have all died because of too much hunting (killing for food), for example the "Passenger Pigeon". Many others are in danger or dead, because people have taken away the places where they lived for wood or farms.

Many species have learned how to get food from people. The number of birds of these species has grown because of it. Seagulls and crows find food from dumping areas. The common pigeon or "Rock Dove" (Columba livia) lives in large numbers in towns and cities all over the world. In North America, House Sparrows (Passer domesticus), Common Starlings (Sturnus vulgaris), and House Finches (Carpodacus mexicanus) are also found in large numbers.

Sometimes people also use birds. For example homing pigeons carry messages (today people sometimes use them for sport). People also use falcons for hunting, and cormorants for fishing. Scientists often use chickens and pigeons to help find answers to their questions. In the past, people in mines often used a Canary to see if there were bad gases in the air.

People often have colorful, particularly tropical, birds (for example, parrots, and mynahs) as pets. Some of these birds are popular because they can copy human talking. Because of this, some people take birds to other countries when it is not allowed.

People can catch some bird diseases, for example psittacosis, salmonellosis, campylobacteriosis, Newcastle's disease, mycobacteriosis, influenza, giardiasis, and cryptosporiadiosis. In 2005, there is an epidemic of bird influenza spreading through some parts of the world, often called avian flu.

Some people have birdboxes in their gardens to give birds a place to nest.