The Christmas Bird Count (CBC) is the National Audubon Society's winter bird census, held every year between December 14 and January 5. Volunteers count every bird they see or hear on one day inside a fixed circle 15 miles across, and a local compiler sends the totals to Audubon. It began on Christmas Day 1900. This page covers how it started, how a count works, and how to join for free, from a backyard feeder or in the field.
Quick read
Next count: the 2026–27 season, December 14, 2026 to January 5, 2027. Each circle picks one day in that window.
Cost: free since 2012.
Sign-up: needed. Find a circle and register with its compiler before count day.
Count dates
| Season | Count period | Notes |
|---|---|---|
| First count (1900) | December 25, 1900 | 25 counts, 27 observers |
| 124th (2023–24) | Dec 14, 2023 – Jan 5, 2024 | Continent-wide results summarized below |
| 126th (2025–26) | Dec 14, 2025 – Jan 5, 2026 | More than 2,800 count circles, per Audubon's launch release |
| 2026–27 (127th) | Dec 14, 2026 – Jan 5, 2027 | Dates given by Birds Canada; Audubon gives Dec 14 – Jan 5 as the yearly window |
Audubon's join pages still linked the 126th count's webinars and guides when this page was written, so check them for 2026–27 updates. The compiler manual says online data entry opens December 14 and must be finished by the end of February.
How a count works
- The circle: the whole count happens inside an established circle 15 miles (24 km) in diameter.
- Fixed center: circles stay in place year to year; a new one may be proposed only where it would not overlap others.
- Sectors (example layout): the compiler divides the circle and gives sector leaders their maps.
- Field party: counts along its route in daylight; some counts add optional night owling.
- Feeder watcher: counts at home inside the circle, arranged with the compiler in advance.
- Count period: December 14 to January 5, inclusive.
- Count day: one calendar day, midnight to midnight.
- Count week: 3 days before to 3 days after count day; extra species are listed as "cw" without numbers.
- Growth: 25 counts in 1900; 2,677 counts completed in the 2023–24 season.
The circle. Each count covers an established circle 15 miles in diameter, and Audubon's compiler manual says the count "must be done entirely within" it. Volunteers follow assigned routes and count every bird they see or hear.
The compiler. Every circle has a compiler who recruits and trains participants, gets permission for private land, plans and scouts routes, and submits the data. Rare birds need documentation for the regional editor. Audubon's press release says all data must go through the official compiler to be included.
The day. Each circle counts on a single 24-hour calendar day, midnight to midnight, within the count period, and the manual asks circles to keep the same weekday or date each year where possible. It asks for at least 8 daylight hours of counting (with exceptions for short-daylight areas and pelagic counts) and says 10 observers are preferred for the best coverage. Birds found in count week but missed on count day can be listed as "cw," without numbers.
Effort counts too. Because "each CBC is a real census," Audubon collects effort data as well as bird numbers. That is why you cannot send in your own CBC list without joining a circle. The FAQ suggests the Great Backyard Bird Count for people who want to count on their own.
History since 1900
Before 1900 many people took part in a holiday "Side Hunt": teams competed to shoot the most birds and mammals. On Christmas Day 1900 the ornithologist Frank M. Chapman, an early officer of the Audubon Society, proposed a "Christmas Bird Census" to count birds instead of killing them.
| Year or season | Milestone |
|---|---|
| Dec 25, 1900 | Chapman and 26 others hold 25 counts, from Toronto, Ontario, to Pacific Grove, California; about 90 species |
| 2000–01 (101st) | 52,471 participants in 1,823 places in 17 countries (Wikipedia) |
| 2012 | The count becomes free; Audubon says it now relies entirely on donations |
| 2012–13 (113th) | 71,531 participants at 2,369 locations (Wikipedia) |
| 2023–24 (124th) | 2,677 counts, 83,186 participants (72,129 field, 11,057 feeder), 40,871,030 birds, 2,380 species |
| 2025–26 (126th) | More than 2,800 circles from Canada to Chile |
The 124th count summary splits the counts as 2,019 in the United States, 470 in Canada and 188 in Latin America, the Caribbean and the Pacific Islands, with 43 new circles. In the US, 7,217 people counted at feeders. In Canada, Birds Canada delivers the count for Audubon and lists "close to 500 circles."
How to join, step by step
- Find a circle. Use Audubon's CBC Circle Finder. In Canada, Birds Canada has you pick a circle on its Circle Finder Map and register.
- Register and contact the compiler well before count day. Taking extra people is "the individual decision of each circle compiler," so a full circle may say no.
- Choose field or feeder. A field count means surveying an area in daylight, alone or in a group. A feeder count needs no binoculars or hiking, but your home must be inside the circle.
- Prepare. Audubon offers a CBC 101 webinar (English, Spanish and French) and quick-start guides. Beginners are welcome: "your compiler will pair you with an expert initially."
- Count on the day. Dress for the weather, bring water and snacks, and record every bird and your hours.
- Report to your sector leader or compiler, not to Audubon. Rare birds need a documentation form.
Single-observer counts are "not allowed" except in unusual circumstances, Audubon's FAQ says. If there is no circle near you, anyone can propose a new one that does not overlap others, but Audubon calls this "a long-term commitment." Questions go to cbcadmin@audubon.org.
If you count from your feeder
Audubon's feeder-watching guidance asks you to:
- Confirm your site with the compiler or sector leader, so field teams don't count your birds twice.
- Record only between midnight and 11:59 p.m. on your circle's count day.
- Log observers and the time you actually spent watching, to the nearest quarter hour.
- Keep the largest number of each species seen or heard at one time; never add visits together.
- Include birds waiting nearby but not birds that only fly over.
- Write "chickadee sp." where Black-capped and Carolina Chickadees overlap and you can't tell them apart. Our chickadee page compares the two.
If your compiler approves eBird for sharing data, follow the compiler's instructions; our eBird for beginners guide covers checklists and counting in eBird.
What the data are used for
Audubon says CBC data have been cited in more than 300 peer-reviewed articles. Combined with the Breeding Bird Survey, they show about a century of population change. They went into the 2019 Science study on the loss of nearly three billion North American birds since 1970, and a 2022 Audubon study of range shifts used 90 years of counts. The US EPA's 2012 report used Audubon's CBC climate work as one of 26 climate-change indicators.
Where sources differ
- The first count. Audubon (27 observers, 25 counts) and Birds Canada (25 counts) agree on the count total. Audubon gives "about 90 species"; Wikipedia gives 90 species and 18,500 birds, a bird total the Audubon history page does not state.
- Canadian circles. The 124th summary lists 470 Canadian counts completed; Birds Canada says "close to 500 circles." One figure counts completed counts in one season; the other describes circles in general.
CBC or GBBC?
| CBC | GBBC | |
|---|---|---|
| When | One day, Dec 14 – Jan 5 | Four days in February; 15 minutes is enough |
| Where | Inside an assigned 15-mile circle | Anywhere |
| Sign-up | Register with a compiler | None |
| Submit | Through the compiler | Merlin or eBird |
Birds you find on count day can also go on a Bird-a-Day streak list.
Before count day
- Circle found and registration done
- Compiler contacted; field or feeder role agreed
- Count date and your sector or route noted
- Feeder watchers: site confirmed inside the circle
- Warm clothes, water, snacks and binoculars if you have them
- Tally sheet ready for species, peak counts and hours
- Rare-bird documentation form requested, just in case
Sources
- History of the Christmas Bird Count — National Audubon Society
- Join the Christmas Bird Count and Join or Start a Christmas Bird Count — National Audubon Society
- Answers to Your Top Questions About the Christmas Bird Count — National Audubon Society
- CBC Compiler Protocol Manual (October 2025, PDF) — National Audubon Society
- Christmas Bird Count Feeder Watching Guidance (PDF) — National Audubon Society
- Join Audubon's 126th Annual Christmas Bird Count (press release, December 14, 2025) — National Audubon Society
- 124th Christmas Bird Count Summary (Cooper Farr, 2024) — National Audubon Society
- Christmas Bird Count — Birds Canada
- How to Participate — Great Backyard Bird Count, birdcount.org
- Christmas Bird Count — Wikipedia