Using data from the North American Breeding Bird Survey (BBS), continental and regional changes in bird populations were estimated for the 2-year periods of 1991-1992 and 1992-1993. These 2-year changes were placed in the context of population trends since 1966. During 1991-1992, 62% of all species exhibited positive continental trend estimates. For species showing significant population trends, 68 increased while 30 decreased. The percentage of species with positive continental trends was reduced to 45% during 1992-1993, when 39 species exhibited significant increases and 60 experienced significant decreases. Over the entire survey period of 1966-1993, 48% of all species showed positive trend estimates, with the number of species showing significant increases and significant decreases at 94 and 104, respectively. The continental and regional percentages were also analyzed for 12 groups of North American birds having shared life-history traits. While many regional patterns existed within these groups, the largest percentages of increasing species were generally found in the Central and Western BBS regions during 1991-1992. The smallest percentages of increasing species were generally evident in the Western BBS Region during 1992-1993.
Additional publication details
The 1992 and 1993 summary of the North American Breeding Bird Survey