Ornithology, the scientific study of birds; a branch of zoology. Ornithologists examine both wild and domestic birds, investigating their anatomy, behavior, evolutionary development, ecology, classification, and species distribution. Much of today's knowledge of birds also comes from amateur bird-watching, which is not only an enjoyable hobby but has also contributed valuable data on the behavior and migration of birds. As a result of such activities, many organizations have been formed to educate the public in the protection and consideration of bird life, including the Royal Society for the Protection of Birds in the United Kingdom and the National Audubon Society in the U.S. The International Ornithological Congress, which originated in Vienna in 1884, is held every four years for amateur bird-watchers and professionals alike. See Bird.