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Road traffic and nearby grassland bird patterns in a suburbanizing landscape.
Forman, Richard1, Reineking, Bjorn1, Hersperger, Anna1, 1
ABSTRACT- An extensive road system with rapidly increasing traffic produces diverse ecological effects that cover a large land area. Our objective was to evaluate one hypothesized widespread effect, i.e., roads with different traffic volumes affecting surrounding avian distributions, and its importance relative to other variables. Grassland bird data for 84 open patches in an outer suburban/rural landscape near Boston were analyzed relative to: distance from roads with 3-8K (3000-8000) to >30K vehicles/day; open-habitat patch size; area of quality microhabitat within a patch; adjacent land use; and distance to other open patches. Grassland bird presence and regular breeding correlated significantly with both distance-from-road and habitat patch size. Distance to nearest other open patch, irrespective of size, was not significant. Similarly, except for one species, adjacent land use, in this case built area, was not significant. A light traffic volume of 3-8K veh/d (local collector street) had no significant effect on grassland bird distribution. For moderate traffic of 8-15K (through street) there was no effect on bird presence, but regular breeding was reduced for 400 m from a road. For heavier traffic of 15-30K (two-lane highway) both bird presence and breeding were decreased for 700 m. For a heavy traffic volume of ≥ 30K veh/d (multi-lane highway) bird presence and breeding were reduced for 1200 m from a road. We conclude that the research frontier of road ecology is a sine qua non for effective land-use and transportation policy.
KEY WORDS: distance-from-road effect, grassland birds, landscape ecology, road ecology