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  North American Breeding Bird Survey Mourning Warbler
  North American Breeding Bird Survey

Abstracts of Published Breeding Bird Survey Summaries: 1994-1995
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 Bruce G. Peterjohn,  John R. Sauer, and William A. Link

 USGS, Biological Resources Division
 Patuxent Wildlife Research Center
 Laurel, MD  20708

 Abstract.  Data from the North American Breeding Bird Survey were used to estimate continental and regional changes in bird populations for the 2-year periods of 1993-1994 and 1994-1995.  These 2-year changes were placed in the context of population trends estimated over the 1966-1995 interval.  The 2-year changes were more positive during the 1993-1994 period, when 54.2% of all species exhibited positive continental trend estimates.  This percentage was reduced to 47.7% during 1994-1995, as compared with 50.2% of all species having positive continental trend estimates over the entire survey period.  In general, the percentage of increasing species in the Central and Western BBS regions was highest during 1993-1994, with a very marked decline in the Western BBS Region during 1994-1995.  The percentage was highest in the Eastern BBS Region during 1994-1995.  The continental and regional percentages of species with positive trend estimates were also analyzed for 12 groups of North American birds having shared life-history traits.  Over the entire survey period, grassland birds remain the species group with the smallest percentage of increasing species.  Trends during these 2-year intervals do not indicate any consistent improvement in the overall declines experienced by grassland birds since the mid-1960s.
Bird Populations, 3:48-66 (1996)


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