Identifying common patterns in diverse systems: effects of exurban development on birds of the Adirondack Park and the Greater Yellowstone Ecosystem, USA.

We examined the impacts of exurban development on bird communities in Essex County, New York and Madison County, Montana by comparing differences in abundance of songbirds between subdivisions and control sites in both regions. We hypothesized that impacts to bird communities would be greater in the relatively homogeneous, closed canopy Adirondack forest of northern New York State than they would be in the more naturally heterogeneous grasslands interspersed with trees and shrubs of the Greater Yellowstone Ecosystem. We examined birds in five functional groups expected to be responsive to exurban development, and determined relative abundance within subdivisions and control sites across these two distinct regions. We found little support for our hypothesis. For birds in the area-sensitive, low nesting, and Neotropical migrant functional groups, relative abundance was lower in subdivisions in the Adirondacks and in Madison County, while relative abundance of edge specialists was greater in subdivisions in both regions. The direction and magnitude of change in the avian communities between subdivisions and controls was similar in both regions for all guilds except microhabitat specialists. These similarities across diverse ecosystems suggest that the ecological context of the encompassing region may be less important than other elements in shaping avian communities in exurban systems. This finding suggests that humans and their specific behaviors and activities in exurban areas may be underappreciated but potentially important drivers of change in these regions.