Many bird species migrate to a cooler climate for reproducing and summer feeding, and then return to a warmer climate for the winter. It is unknown exactly how birds are able to navigate accurately , but many people are studying this mystery of how birds know where to fly. 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.