Two Turtle Doves and a Partridge in a Pear Tree: The Christmas Bird Count


Home / Two Turtle Doves and a Partridge in a Pear Tree: The Christmas Bird Count
Photo by Christi Norman.

Birdwatchers count and track birds without hurting them.Photo by Christi Norman.

In the last days of the old year and the first days of the new, birders across the country wrap their binoculars around their necks and set out to count their winged friends.

It’s time for the Christmas Bird Count, over one hundred years old and still going strong.

This venerable event began in 1900 with a note from Frank Chapman in Bird Lore, the Audubon Society’s magazine. In the 19th century, hunters ventured out on Christmas day to shoot birds, often in competitive events called “side hunts,” in which hundreds of birds were slaughtered.

Chapman suggested that bird lovers start “a new kind of Christmas side hunt, in the form of a Christmas bird-census.

On December 25, 1900, 27 birders conducted 25 bird counts, counting 90 species.

The 113th count has just completed, taking place from December 14, 2012 to January 5, 2013, and more than 50,000 birders participated. Based on recent results, they may have recorded around 70 million birds.

Four and Twenty Blackbirds: How to Count the Birds

Volunteers head out in the early morning of a designated day—in Seattle, Washington, that’s December 29 of every year. They count every bird they encounter (either see or hear) in a designated circle 15 miles (24 km) in diameter. Seattle’s circle is broken up into smaller units; the counters come together at the end of the day to share their count totals over a potluck supper.

Expert birders lead the count; beginners are welcome to join in. Some still like to inject a little competition into the event and stay out into the waning evening light to add to their species count.

The More the Merrier: More People Gather More Reliable Data

How can scientists be sure that these counts are reliable?

The very fact that so many people participate helps by providing a “favorable signal-to-noise ratio”—errors probably cancel themselves out—and the data is reviewed by experts, so obvious errors can be eliminated (a summer migrant in northern latitudes in the winter, for example).

Ecological Health Indicators: The Canary in the Mineshaft

Birds are probably the most visible of all the wild species with which we share the planet. They are found in all habitats and many live close to us in our cities, towns, and farms—sometimes even in or on our houses. A decline in numbers of a bird species can be an early warning signal of habitat loss and degradation.

Christmas Bird Count volunteers count birds in the same place every year—the designated circle—and at the same time—mid-winter. Over time this consistent count can build up an accurate picture of where the birds are and how well a species is doing: is it increasing, declining, or staying the same. Scientists can follow up on interesting results (such as a fall in numbers) with more focused studies to figure out what is happening.

When the counts showed that American Black Duck numbers were falling, for example, conservation measures were put in place to protect the species.

The counts can also add to our knowledge of other events, such as climate change; they show that over half of America’s 305 bird species are moving north (by 35 miles, on average) as temperatures increase across the continent.

Find a Bird Count Near You

The Christmas Bird Count is the world’s oldest citizen science project. The more people that participate the better—find a bird count near you through Audubon Magazine.

The success of this Bird Count has spurred other counts, including the Great Backyard Bird Count (GBBC) coming up in February. If you missed the Christmas count in your area, you can sign up at GBBC.


GBBC. The Great Backyard Bird Count. (2013). Accessed January 3, 2013.

Bonney, R., C. Cooper, J. Dickinson, S. Kelling, T. Phillips, K. Rosenberg, and J. Shirk.  Citizen Science: A Developing Tool for Expanding Science Knowledge and Scientific Literacy. (2009). Bio Science 59:977-984. American Institute of Biological Sciences. Accessed January 3, 2013.

Butcher, G., D. Niven, and J. Sauer. Using Christmas Bird Count Data to Assess Population Dynamics and Trends of Waterbirds. (2005). Accessed January 3, 2013.

Gregory, R. Birds as biodiversity indicators for sustainability, a pan-European strategy. (2003). European Bird Census Council. Accessed January 3, 2013.

National Audubon Society. State of the Birds: Birds and Climate Change(2009). Accessed January 3, 2013.

Audubon Magazine. Get Involved in the Christmas Bird Count – Find a Count Near You. (2013). Accessed January 3, 2013.

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