710710.fig.001
Figure 1: Our study area (29–47°N, 67–95°W) divided into three regions based on classifications used by the Breeding Bird Survey (http://www.pwrc.usgs.gov/bbs/) and the Environmental Protection Agency (Level III Ecoregions; http://www.epa.gov/wed/pages/ecoregions/level_iii_iv.htm).