Bird

Birds, are a group of vertebrates that are part of the class, Aves. They are described by their feathers, toothless beaked jaws, laying hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong but also light-weight skeleton. There are about ten thousands living species of birds, which more then half of them, are passerines. Birds have wings, which gave birds the ability to fly though through evolution, some lost the ability such as ratites and penguins.