Do you know what makes a bird different from other animals? Is it the pretty colors?
No -- other animals, like fish and insects, come in all sorts of beautiful colors too.
Is it the bill or beak?
No -- other animals, like the duck billed platypus (a mammal), have bills too.
Is it the eggs?
No -- other animals, like fish, amphibians, reptiles, insects and even some mammals, hatch from eggs as well.
Is it the wings?
No -- other animals, like insects and some mammals, have wings.
Then what is it!? Feathers!
All birds have feathers and birds are the only animals that do!
Nevertheless, feathers are not the only features of a bird. Other important features for birds are wings and hollow bones with air sacs in them. This makes them lighter and makes flight easier. Birds also lay eggs, like reptiles, however they are warm-blooded, like mammals.
Feathers are made of keratin. This is the same stuff that fingernails are made of.
Feathers are important to birds because they keep them warm, help them to fly, and provide camouflage. Hollow bones are important because they help make the bird light enough to fly. Of course wings are important to flying as well.
Birds are bipedal: they have two legs which are often covered with scales. They have a hard beak with no teeth.
According to Wikipedia there are more than 9000 different species of birds. Birds are found on every continent of the world. Birds of different types can live in freezing cold environments, and others can live in hot deserts. Birds live in forests, in grasslands, on cliff faces, in river banks, on stony sea shores, down mine shafts and in the roofs of houses.
There are all sizes of birds. Hummingbirds are some of the smallest birds, while ostriches are some of the biggest. Different types of birds eat different foods. Most birds are carnivorous meaning that they eat flesh, at least some of the time. Many birds live on insects or on fish. Some eat small reptiles and mice. Birds of prey...