What Is the Christmas Bird Count?

The Christmas Bird Count is an annual large-scale bird census organized by the National Audubon Society—a U.S.-based conservation organization—that takes place in early winter across the Western Hemisphere. It enlists volunteer bird-watchers to count birds within a 24-km- (15-mile-) diameter circle at specified locations on a chosen date between December 14 and January 5. Started in 1900, it is one of the longest-running community science programs in the world.

When did it start?

Christmas side hunts were a popular 19th-century North American tradition. Hunting parties, or sides, would go out on Christmas Day and compete to kill the most animals—typically birds. Amid growing concerns about diminishing bird populations at the dawn of the 20th century, American ornithologist Frank Chapman suggested an alternative holiday tradition—counting birds on Christmas instead of hunting them. On December 25, 1900, 27 bird-watchers across 25 locations in North America conducted bird censuses, or “counts,” marking the beginning of the annual Christmas Bird Count.

The “who” and “where” of the count

The first census documented birds at sites between Pacific Grove, California, and Toronto. Since then, the number of census locations and participants has increased substantially, and the census now takes place in 21 countries and territories in the Western Hemisphere, including those in Latin America, the Caribbean, and the Pacific Islands. The 125th Christmas Bird Count, in 2024–25, had 83,109 volunteers conducting censuses in 2,693 counting circles.

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Birders of all experience levels may volunteer in the count. With support from count-circle compilers, participants record the birds they see or hear over the course of a day along routes and at bird feeders within the designated circles. In Canada the count is administered by Birds Canada in collaboration with the National Audubon Society.

How is the data used?

Data generated by the Christmas Bird Count informs scientists about the population health, community ecology, winter distribution, migratory patterns, range variations, and invasion dynamics of birds of the Western Hemisphere. The continuity of this census for more than a century has yielded vital information on how birds of the Americas have fared over the years. The data complements information gathered by other bird surveys, such as the North American Breeding Bird Survey, to provide a more holistic overview of North American avifauna. Scientists use Christmas Bird Count data to determine the effects of climate change on bird populations, habitats, and ranges. The statistical models developed based on the count data also help scientists propose actionable conservation strategies.