The BBS is a long-term, large-scale, international avian monitoring program initiated in 1966 to track the status and trends of North American bird populations. Each year during the height of the avian breeding season, (June), thousands of dedicated participants skilled in avian identification follow a rigorous protocol, to collect bird population data along 4100 roadside survey routes located across the continental U.S. and Canada. Trend estimates and all raw data are currently available for more than 420 bird species. Once analyzed, BBS data provide an index of population abundance that can be used to estimate population trends and relative abundances at various geographic scales for use by conservation managers, scientists, and the general public..