Data from the North American Breeding Bird Survey were used to estimate continental and regional changes in bird populations for the 6-yr period 2003-2008 and the 2-yr period 2007-2008. These short-term changes were placed in the context of population trends estimated over the 1966-2008 interval. Across the entire survey area, a higher proportion of species exhibited positive growth during 2003-2008 (64%) than during the long-term (46%) or the more recent 2-yr-term (39%). The 2003-2008 growth occurred relatively evenly across the Western, Central, and Eastern BBS regions, with 59%, 66%, and 61% of all species increasing, respectively. We additionally evaluated the proportion of species with positive trend estimates in each of 12 life-history based groupings at continental and regional levels. Survey-wide, birds in the grassland guild demonstrated the lowest proportion of positive trends over the entire survey period (21% increasing), with significant declines occurring in both the Eastern and Western regions (5% increasing and 18% increasing, respectively). Birds in the wetland breeding guild exhibited the greatest proportion of positive trends, with a significant number of increasing species (between 77-90%) occurring in all three BBS regions during 2003-2008.
Additional publication details
The 2003-2008 summary of the North American Breeding Bird Survey