The Christmas Bird Count (CBC) is a census of birds in the Western Hemisphere, performed annually in the early Northern-hemisphere winter by volunteer birdwatchers and administered by the National Audubon Society. The purpose is to provide population data for use in science, especially conservation biology, though many people participate for recreation. The CBC is the longest-running citizen science survey in the world.

Birdwatching, or birding, is the observing of birds, either as a recreational activity or as a form of citizen science. A birdwatcher may observe by using their naked eye, by using a visual enhancement device like binoculars or a telescope, by listening for bird sounds, or by watching public webcams.