North American Breeding Bird Survey (BBS)


The BBS is a cooperative effort between the U.S. Geological Survey's Patuxent Wildlife Research Center, Environment Canada's Canadian Wildlife Service, and the Mexican National Commission for the Knowledge and Use of Biodiversity to monitor the status and trends of North American bird populations. Following a strict protocol, BBS data are collected by dedicated participants along randomly established roadside routes throughout the continent. Professional BBS staff works closely with researchers and statisticians to compile and deliver these population data and trend analyses on more than 400 bird species, for use by conservation managers, scientists, and the general public. Each year during the height of the breeding season, participants collect bird population data along survey routes. Each route is approximately 24.5 miles long with stops at approximately 0.5-mile intervals. At each stop, a 3-minute point count is conducted, during which every bird seen within a 0.25-mile radius or heard is recorded. Surveys start one-half hour before local sunrise and take about 5 hours to complete. Approximately 3000 routes are sampled annually. These data provide indices of population abundance that are used to estimate population trends and relative abundances at various geographic scales.


Established in 1966, the BBS is arguably the largest and longest running data set available for breeding birds.  In addition to its large temporal and geographic extents, keys to BBS success include a scientifically rigorous sampling design, a relatively simple field protocol, and a highly skilled and dedicated volunteer workforce. Moreover a variety of online resources are available, including raw data, summary estimates of population change by species, graphs of annual indices, abundance maps, trend maps, and online analysis modules that permit estimation of population change by species for any region and time period of interest.


The BBS is effective in estimating population trends for about 420 species. However, quality of information varies widely among species, and the BBS tends to provide imprecise results for species 1) associated with habitats that are underrepresented along roadsides (e.g. wetlands, forest interiors); 2) that are nocturnal/crepuscular (e.g. owls, nightjars); 3) that are less detectable (e.g. some raptors); and 4) that are rare or with restricted distributions. The roadside count-based design of the BBS has been criticized because roadsides may not be representative of the entire landscape, and the point count protocol employed by the BBS does not allow for estimation of detection probabilities.

Examples of use

The BBS provides scientifically credible population measures to inform sound avian research, conservation and management actions. In addition to alerting managers of widespread declines of neotropical migrants in 1989 and subsequent grassland bird declines, spurring further research and conservation action on those taxa, BBS trends along with other indicators are used by Federal and State agencies, and many others, to assess national and regional avian conservation priorities. Over 450 scientific publications have relied heavily, if not entirely, on BBS data. See the BBS Bibliography for more data use examples (

For more information or to participate and sign up for a route: