Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network

Open Access. Powered by Scholars. Published by Universities.®

PDF

Portland State University

Biology Faculty Publications and Presentations

2003

Bird populations -- Estimates

Articles 1 - 1 of 1

Full-Text Articles in Entire DC Network

Avian Population Trends Within The Evolving Agricultural Landscape Of The Eastern And Central United States, Michael T. Murphy Jan 2003

Avian Population Trends Within The Evolving Agricultural Landscape Of The Eastern And Central United States, Michael T. Murphy

Biology Faculty Publications and Presentations

State-level Breeding Bird Survey (1980-1998) and U.S. Department of Agriculture statistics were used to test the hypothesis that changes in agricultural land use within the eastern and central U.S. have driven population trends of grassland and shrub habitat birds over the past two decades. The degree to which population trends differed between grassland and shrub habitats was evaluated with respect to migratory and nesting behavior. Grassland birds declined significantly between 1980 and 1999, but, on average, shrub habitat species did not. Grassland-breeding, long-distance migrants exhibited the strongest negative trends. Most species (78%; n = 63) exhibited at least one significant …