Many bird species migrate to a cooler climate for reproducing and summer feeding, and return to a warmer climate for the winter. It is unknown exactly how birds are able to navigate accurately. The fastest two-legged runner on earth is the flightless ostrich , which is also the largest bird. They use their beaks to catch bugs, worms, small mammals, fish, fruit, or nectar. Birds play an important part in the control of insects, the dispersal of seeds, and the pollination of flowering plants.
Birds bear their young in hard-shelled eggs.
Birds are also amniotes, a group that includes the mammals, birds, dinosaurs, and reptiles. There are about 9,000 different species of birds, divided into 24 orders and 146 Families. Many songbirds are becoming scarcer.