Birds belong to the biological class Aves and live virtually everywhere on Earth. There are about 9,000 different species of birds, divided into 24 orders and 146 Families . Early birds, like Archaeopteryx , had teeth in their mouth and claws on their wings. Birds sing beautiful and diversified songs . Many songbirds are becoming scarcer every year.
Songbirds have a vocal organ called the syrinx located in the throat.
The muscular syrinx has two halves that each vibrate to produce songs, so the bird can sing two notes at a time. To sing, a bird blows air from the lungs through the syrinx. The part of a bird's legs that bends backwards when it walks is the ankle. In order to fly, birds need a lot of oxygen, which they get by breathing air using lungs. They also need a strong circulatory system, including a powerful heart in order to circulate the oxygen.