Audubon Christmas Bird CountsEntry ID: brdpwrc0006
Abstract: Audubon link: http://www.audubon.org/
The first Christmas Bird Counts (CBCs) were conducted in 1900 in response to a
suggestion made in the National Audubon Society's magazine Bird-Lore.
Twenty-seven individuals responded by spending several hours on Christmas Day
in their neighborhood, counting all of the birds they observed or heard. This
survey has been coordinated by the National Audubon ... Society ever since, and has
become the oldest continuous wildlife survey in North America.
CBCs quickly expanded into entire day censuses, when single observers covered
as much territory as possible counting all of the individuals that could be
positively identified. While the number of hours in the field and miles covered
varied from individual to individual, the intention was that repetition of
these surveys would allow for the monitoring of trends in bird populations of
These single observer counts quickly evolved into a more organized effort,
where groups of people would count birds in a larger area during a single day.
By the 1920s, most of the CBCs consisted of group counts rather than censuses
by individuals. Unfortunately, as CBCs evolved into group efforts, there was
little consistency in some of the aspects of the methodologies followed by
these counts. The area covered varied from CBC to CBC, as did the count date
and level of coverage. While these differences prevented meaningful comparisons
of the results between CBCs, the data from single CBCs could still provide
useful information on the status and trends of populations within each area.
In order to provide more useful results from CBCs, the National Audubon Society
implemented uniform standards beginning in the late 1950s. This methodology is
still in use today.
USES OF CBC DATA CBC data has received considerable use during recent decades,
primarily directed towards two topics: winter distribution patterns and
population trends. Many other potential uses exist for these data, such as
showing patterns of winter species diversity over large geographic scales, but
these studies would require a better understanding of the biases associated
with the data before they could be conducted.
These data provide a wealth of information on the early winter distributions of
birds in North America, and geographic patterns in their relative abundances.
Root (1988) used CBC data in preparation of an atlas of winter bird
distribution. Other distribution maps have been developed by others.
These data have also been widely used to establish the population trends of
birds. Given the lack of consistency of coverage, temporal changes in effort,
and other problems, the estimation of trends using CBC data has remained
controversial (see Analytical Considerations section below). Some preliminary
analyses have been conducted, but additional studies are needed in order to
better understand the potential biases associated with CBC data and how to
estimate population trends with these data.
AVAILABILITY OF CBC DATA At this time, only the CBC data between the winters of
1900-1901 through 1908-1909, 1959-1960 through 1988-1989, and 1994-1995 have
been computerized. An effort is underway to computerize the remainder of the
database, hopefully, the entire CBC database will be computerized and readily
accessible within the next 1-2 years.
CBC census data organized by state is available
(Click for Interactive Map)
Data Set Citation
Dataset Originator/Creator: National Audubon Society
Dataset Title: Audubon Christmas Bird Counts
Dataset Release Date: 1996-01-01
Dataset Release Place: New York, NY
Dataset Publisher: National Audubon SocietyOnline Resource: http://www.mbr-pwrc.usgs.gov/bbs/cbc.html
Dataset Title: Audubon Christmas Bird Counts
Dataset Publisher: National Audubon SocietyOnline Resource: http://www.audubon.org/bird/cbc/
Start Date: 1990-01-01Stop Date: 1996-01-01
ISO Topic Category
Quality Volunteer generated, but thoroughly reviewed in field. Reviewed by 33 regional
editors, many of whom are part of the rare birds committee.
Completeness varies depending on geographic area in question
Access Constraints none
Use Constraints none
Role: TECHNICAL CONTACT
Email: cbcadmin at audubon.org
545 Almshouse Rd
Province or State: PA
Postal Code: 18974
Role: DIF AUTHOR
Phone: (301) 614-6898
Email: Tyler.B.Stevens at nasa.gov
NASA Goddard Space Flight Center Global Change Master Directory
Province or State: MD
Postal Code: 20771
National Audubon Society. 1996. Christmas Bird count issue. in 96th Christmas Bird Count National Audubon Society Field Notes, Vol. 50 No. 4
Sauer, J. R., S. Schwartz, and B. Hoover. 1996. The Christmas Bird Count Home Page. Version 95.1. Patuxent Wildlife Research Center, Laurel, MD
Creation and Review Dates
Last DIF Revision Date: 2007-02-15