Birds are flying animals interesting. They are warm-blooded vertebrates and animals. They belong to a class aves and they can be found all over the world. Bird breath with their air bags. Aside from being an organ of respiration, the air bag can also enlarge or reduce their weight when flying or swimming. There are many types of birds. Earth birds have special characteristics. They have a different morphology according to their food and habitat. Some of them feed on seeds, pollen, fish or meat. There are some species that live in the soil and the others live in the water. Land birds live in their nests