Answers to your top questions about the Christmas Bird Count

What is the Christmas Bird Count? 

Frank Chapman and 26 other conservationists initiated the Christmas Bird Count (CBC) as a way of promoting conservation by counting, rather than hunting, birds on Christmas Day of 1900. Some counts have been running every year since then and the CBC now happens in over 20 countries in the western hemisphere!  Read about the history here.  Now a long-standing program of the National Audubon Society, with over 120 years of community science involvement, it is an early-winter bird census, where thousands of volunteers across the U.S., Canada (where Audubon partners with Birds Canada), and many countries in the Western Hemisphere go out over a 24-hour period on one calendar day to count birds. 

When does the Christmas Bird Count happen?

All Christmas Bird Counts are conducted between December 14 to January 5, inclusive dates, every year. Each circle compiler will choose a single calendar day within those dates and your CBC birding is done on only one calendar day for each circle.

Is Participation in the CBC free? 

Yes, participation is free. However, you will need to provide your own transportation, binoculars and weather appropriate clothing.  

How does participation work?

There is a specific methodology to the CBC, and all participants must make arrangements to participate in advance with the circle compiler but the CBC is open to all!

Each count takes place in an established 15-mile diameter circle, and is organized by a count compiler. Count volunteers follow specified routes through a designated 15-mile (24-km) diameter circle, counting every bird they see or hear all day. It's not just a species tally—all birds are counted all day, giving an indication of the total number of birds in the circle that day.

Birders of all skill sets are involved in the CBC. If you are a beginning birder, your compiler will pair you with an expert initially.   

If your home is within the boundaries of a CBC circle, then you can stay at home and report the birds that visit your feeder on count day as long as you have made prior arrangement with the count compiler.

Can I just do my own CBC and send you my data? 

No. Since each CBC is a real census, effort data are collected as well as bird numbers, and since the 15-mile diameter circle contains a lot of area to be covered, single-observer counts (except in unusual circumstances) are not allowed. To participate in the CBC, you will need to join an existing CBC circle by contacting the compiler in advance of the count day.

As an alternative, you may be interested in getting involved in the Great Backyard Bird Count (GBBC) organized by Audubon, the Cornell Lab of Ornithology and Birds Canada. It takes place President's Day weekend each February, and you can count the birds each day in your backyard/community and then enter the results online. For more information on the GBBC, visit Audubon’s GBBC page.

Why do some Christmas Bird Count circles not accept additional participants? 

Accepting additional participants is the individual decision of each circle compiler and is based on a number of factors, including the number of participants already committed to the count, potential pre-arranged access to restricted areas, the amount of area already covered, and the compiler's available time.

I cannot find a circle near me, can I set up my own circle?

Anyone can propose a new  CBC circle as long as there is space to add one without overlapping other circles (Overlapping circles established previous to 2001 are exempted and those compilers coordinate closely). Please make sure to read the requirements and follow the application process here. Be aware that establishing a new circle is a long-term commitment.

What is the role of a Compiler? 

The count circle compiler is responsible for recruiting, training and guiding participants on the count and summarizing and submitting data. Read about the responsibilities of a compiler on the compilers resource page and the compiler manual here. You can also learn how compilers plan a CBC count by reading The Art of the Christmas Bird Count by Alan Contreras, longtime compiler and former regional editor of count circles in Oregon. You could become a compiler by getting involved in your local count circle(s) and learning where you can help, or you can propose a new count circle. 

How is the Christmas Bird Count funded?

The Christmas Bird Count relies 100 percent on donations since becoming free to participate in 2012. Audubon provides support to compilers and volunteers, to manage the historic database, and to fund the technology to make historic data available to researchers. The data collected by CBC participants over the past century have become one of only two large pools of information informing ornithologists and conservation biologists how the birds of the Americas are faring over time. Help us keep the program free and to ensure the future of the program. Please make a donation today.

How are data from the Christmas Bird Count used?

CBC data have been used in hundreds of analyses, peer-reviewed publications, and government reports over the decades. Consult our bibliography page or use Google Scholar to search for research using CBC data. Yearly summaries of CBC data submitted by each circle compiler can be found through this page.

Audubon’s quantitative ecologist updates the CBC Population Trends periodically which can be viewed and downloaded from this page. 

A few recent publications using CBC data include the following:
A 2021 study published in the Journal of Wildlife Management was conducted by the National Audubon Society and Clemson University’s James C. Kennedy Waterfowl and Wetlands Conservation Center. This publication showed populations of 16 common duck species that winter in the Southeastern U.S. have shifted northward over the past 50 years due to temperature changes attributed to climate warming. A 2019 publication lead by Audubon presented a new CBC data modeling approach that increases the spatial resolution of trend estimates that can provide reasonable large-scale trend estimates for users interested in general patterns, while also providing higher-resolution estimates for examining correlates of abundance trends at finer spatial scales, which is a prerequisite for tailoring management plans to local conditions.