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

Abstracts of Published Breeding Bird Survey Summaries: 1990-1991
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 Bruce G. Peterjohn
 U.S. Fish and Wildlife Service
 Office of Migratory Bird Management
 Laurel, Maryland 20708
 John R. Sauer
 U.S. Fish and Wildlife Service
 Patuxent Wildlife Research Center
 Laurel, Maryland 20708

  Abstract.  The North American Breeding Bird Survey (BBS) was used to estimate continental and regional changes in bird populations during 1989-1990 and 1990-1991, placing these short-term changes within the context of population trends since 1966. For the entire survey area, 51.7% of the species exhibited increases in population size during 1989-1990, reversing the decreasing tendency exhibited by the majority of species during 1988-1989. A similar percentage (51.4%) of species with increasing populations was noted during 1990-1991. These percentages were also analyzed for 12 guilds of North American birds and 3 broad geographical regions.  Many regional patterns exist in these population changes, reflecting the variability inherent in short-term population fluctuations.  Two-year (1989-1990 and 1990-1991) changes and long-term (1966-1990) continental trends are provided for 255 species.

Bird Populations, 1:1-15 (1993)


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