The BBS is a large-scale survey of North American birds. It is a roadside survey, primarily covering the continental United States and southern Canada, although survey routes have recently been initiated in Alaska and northern Mexico. The BBS was started in 1966, and the over 3,500 routes are surveyed in June by experienced birders.
The primary objective of the BBS has been the estimation of population change for songbirds. However, the data have many potential uses, and investigators have used the data to address a variety of research and management objectives. In the Home Page, we summarize results from the BBS, and supplement the results with pictures of birds and other species information.
The CBC is an early-winter survey of birds. Although counts occur in Central and South America, most CBCs occur in North America. The sample area for a count is a circle that is 15 miles in diameter, and varying numbers of volunteers count all birds they see in the circle during a single day, which is within 2 weeks of 25 December. (Butcher 1990)
Although this analysis only considers the interval 1959 - 1988, the CBC was begun in 1900. The number of circles and participants has changed dramatically since the early years. Butcher (1990) notes that 1,508 circles were surveyed in 1986-1987. Unfortunately, the number of birds counted is a function of effort, and analysis of change over time must incorporate some effort adjustment (Butcher and McCulloch 1990). In this analysis, we standardized the counts to birds/100 party hours. More research is needed into methods of adjusting counts.
Each year, American Birds publishes a summary of the previous years count (e.g., American Birds 47(4):1-1026) that notes interesting features of the counts and summarizes birds, effort, and volunteers for each circle. Also, numerous articles have appeared in American Birds that summarize data for individual species and groups of species. Root (1988) has summarized patterns of regional relative abundance for wintering North American birds.
You can access information on bird species either by category (e.g. relative abundance maps, regional trend estimates, etc.) by clicking on the appropriate category icon, or by species (e.g., Bobolink) by clicking on the species account icon.
Categories of Information include:
Relative abundance maps,
Regional trend estimates,
Annual indices of abundance, and
Maps of population change.
Each of these categories has an icon that can be selected to display species information. For example, to examine a relative abundance map for Bobolink, click on the icon associated with "Abundance Maps" on the Home Page. You will then be presented with a list of species. Scroll down the list and click on "Bobolink," and an abundance map will be displayed.
Species Information:All of the categories of information can also be accessed through the species accounts. Each species has an account, which can be accessed either from the icon on the main menu of the Home Page or from any of the categories of species information. The accounts provide a means for accessing all information for a particular species directly, rather than having to select the species separately on the list for each category.
Analysis of Groups of Species: We summarize the overall patterns of population change and species richness for several groups of species of ecological and management interest.
Analysis and interpretation of BBS data is tricky, because the survey incorporates information from a huge geographic area and the survey varies greatly in quality of information over the area. To document some of the problems with the analyses of BBS data, and help you interpret the results presented on the Home Page, we provide a series of help files that provide information on the survey, discuss problems with its analysis, and tell you how the presented information should be interpreted. We suggest you read the help files for each category of information before looking at the results.
We welcome comments on the home page. We intend to improve it as new methods for summary of survey data are developed, and in response to user feedback. We caution that, as always in data analyses, the possibility exists for errors in the analyses and summaries.
Although these data have been processed successfully on a computer system at the National Biological Service, no warranty expressed or implied is made regarding the accuracy or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. It is strongly recommended that these data are directly acquired from a National Biological Service server, and not indirectly through other sources which may have changed the data in some way. It is also strongly recommended that careful attention be paid to the contents of the metadata file associated with these data. The National Biological Service shall not be held liable for improper or incorrect use of the data described and/or contained herein.
So, these data are provided "as is" and without any express or implied warranties, including, without limitation, the implied warranties of merchantability and fitness for a particular purpose. Also, use of trade names or commercial products in this home page is solely for the purpose of providing specific information, and does not imply recommendation or endorsement by the U.S. Government.
Literature Cited Butcher, G. S. 1990. Audubon Christmas Bird Counts. Pp. 5-13 in J. R. Sauer and S. Droege, eds. Survey designs and statistical methods for the estimation of avian population trends. U.S. Fish Wildl. Serv. Biol. Rep. 90(1). Butcher, G. S., and C. E. McCulloch 1990. The influence of observer effort on the number of individual birds recorded on Christmas Bird Counts. Pp. 120-129 in J. R. Sauer and S. Droege, eds. Survey designs and statistical methods for the estimation of avian population trends. U.S. Fish Wildl. Serv. Biol. Rep. 90(1). Root, T. 1988. Atlas of wintering North American birds. University of Chicago Press, Chicago, Il.