While the actual number of bird species is unknown since new species continue to be discovered, there are approximately 10,500 known species of birds in the world, according to the International Ornithologists’ Union. There are approximately 21,000 subspecies of birds.
Birds are found virtually everywhere on earth, and have adapted to each unique environment. In some cases, certain species are found only in a very small area, while others have a range that spans large parts of the globe.
Each species is unique in appearance and in its adaptation to the environment. Migratory birds often cross great distances across the ocean, and they have even been found in Antarctica.