There are about 9000 species of birds, with 24 orders and 146 families. Scientists believe that birds evolved from reptiles and dinosaurs. Birds are found throughout the world, from the tropics to polar regions. One unique characteristic of many birds is their tendency to migrate. This means that the birds move from colder to warmer areas as the winter approaches.
Birds can be both helpful and harmful to man.
They are helpful as they frequently eat harmful insects. They provide food for man. They are pets and can be very decorative. They are harmful when they eat crops and kill animals. The study of birds is ornithology.