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Christmas Bird Count

Photo credit: Jane Gamble

Citizen scientists are laypeople who contribute to science by participating in projects that generate useful data. One way folks help the scientific community is through the Christmas Bird Count (CBC) sponsored by the National Audubon Society. Centuries ago, this event started as Christmastime hunting expeditions where tallies of the day’s catch were registered. People recognized the counterproductive impact of killing their cherished subjects, so by 1900 a parallel count with a change to scoring live field observations began.

This song sparrow (Melospiza melodia melodia), perched on a swamp rose (Rosa
palustris) branch, is a common species that a novice might mistake for any of the other “little brown birds.” With practice, folks learn to distinguish the different species and appreciate the niches filled by the particular birds.

Today, a typical CBC scenario falls within a 15-mile-wide circle. That area is further divided into sectors where an experienced birder leads a party around a defined patrol route. Novices are paired with knowledgeable birders. Party members count the bird species and numbers (or estimates within a flock) as they tour their designated subsection. Birds seen or heard when doubling back on a trail are not counted unless the species is new to the day’s list. Parties might split up to cover more ground, but at least one skilled birder is in each subgroup. Some people participate by documenting birds visiting a birdfeeder, though this method creates a bias for seed and/or mealworm-eating birds and could omit other avian members such as scavengers and waterfowl. All observations are recorded within a single day from midnight to midnight, on a specific date, rain or shine. CBC data are used to analyze trends and environmental wellbeing.

The Smithsonian Museum of Natural History houses the taxidermy mount of Martha, the world’s last passenger pigeon, who died in 1914.

Never take any species for granted, regardless of how common it appears. A former D.C. area resident, the passenger pigeon (Ectopistes migratorius), numbered more than four billion birds. With 20 percent of all North American birds being passenger pigeons, this species was the most abundant bird on the continent. Second only to humans, these doves influenced their environment more than any other single animal species. Hunting and habitat destruction pummeled the massive passenger pigeon population to extinction within several decades.

Population surveys help scientists spot and stop other threats to birds. For instance, discovering the link among the pesticide DDT, bioaccumulation, and severe declines in top predatory birds led to this pesticide’s ban. The following years saw hawks, eagles, pelicans, and other meat-eating birds begin to recover. Population monitoring is a tool that scientists use to gauge new, emerging threats, such as climate change, manmade obstacles (e.g., glassy skyscrapers and wind turbines) that impede migration, and invasive species overtaking natural areas. Bird counts also help biologists see the positive impacts of habitat restoration projects and safer architectural designs. True to the metaphor, bird populations are a “canary in the coalmine” for environmental health.

The best way to learn bird identification is through field experience and bird walks. A knowledgeable birder, a naturalist, or even an ornithologist leads these treks. You’ll learn how to identify different species by their appearance, movement, behavior, and calls.

Organized bird walks are held at several local parks. Here are two free, regularly scheduled walks:

  • Friends of Dyke Marsh host bird walks every Sunday morning at 8 a.m., starting from the Belle Haven picnic area.
  • Huntley Meadows Park walks occur every Monday morning, beginning at 8 a.m. in the winter and 7 a.m. April through October. Meet at the main entrance.

A big “thank you” goes to Larry Cartwright—compiler of the Washington, D.C., CBC—for sharing details about the count. Contact him at for more information, checklists, or about joining a December 18, 2021, CBC party (which includes the Dyke Marsh sector) or conducting a birdfeeder survey. The count at Huntley Meadows will take place on Sunday, January 2, 2022. To volunteer, contact compiler Kurt Gaskill at or 703-768-2172.

For other regional 2021 CBC sectors, dates, and the compilers’ contact details, see page 3 of the Northern Virginia Bird Club’s newsletter.

References and Bibliography:

Bodio, Stephen J. Spring 2014. A tale of three superdoves. Living Bird 33(2):28-35.

Margonelli, Lisa. January 27, 2016. When birders with binoculars trump supercomputers. Zócalo Public Square.

National Audubon Society’s CBC webpage:

North American Bird Conservation Initiative. 2017. State of the Birds.

Northern Virginia Bird Club. November 2017. Christmas Bird Counts in Northern Virginia. The Siskin 62(4):3.

Randall, Johnny. November 11, 2017. Invasive Plants Are NOT for the Birds.

Souder, William. September 2014. 100 years after her death, Martha, the last passenger pigeon, still resonates. Smithsonian Magazine 45(5).

Author Greg Sykes is a biologist and a volunteer site leader with Fairfax County Park Authority’s Invasive Management Area program.