Birds are also known as Aves or avian dinosaurs. Have wings, feathers, two legs and four chambered heart. They can fly in the sky. In addition, they come in many different colors and sizes from small like the humming bird all the way to the large ostrich. Furthermore, birds lay eggs and have chicks. There are ten thousand species of birds in the world. Some birds can swim like penguins. Others can speak 200 human words like the African Grey Parrot. Finally, most birds stay on trees at night.