From Audubon Pennsylvania:
Ridgetop Important Bird Areas, Raptors, and Wind Turbines
Excerpt: Audubon Pennsylvania stands behind the USFWS in calling for three years of pre-construction monitoring, as well as post-construction monitoring and ongoing mortality and risk assessment, conducted by agency biologists and/or those independent of industry. … Multi-year pre-construction monitoring is critical because of annual variation in migration routes, due to variation in bird species distribution, weather fronts, and resulting wind conditions.
Audubon Pennsylvania recommends to avoid siting turbines on ridgetops that concentrate raptors during spring and fall migration…
In addition, Audubon Pennsylvania advocates the protection of unfragmented forests, Important Bird Areas (IBAs), areas supporting federally and state Threatened and Endangered species, and Landscape Conservation Areas (PA Natural Heritage Program - www.dcnr.state.pa.us/forestry/pndi). More appropriate turbine sites would be post-industrial (brownfield) sites, away from major migratory corridors. We seek to minimize fragmentation of intact forest blocks, as PA currently supports large breeding populations of forest birds. The fragmentation of large forest blocks is listed as a bird population stressor in many of our IBA conservation plans (the plans can be found at http://pa.audubon.org). Siting wind turbines on "brownfields" (post-industrial sites) rather than large, intact forest blocks would minimize such fragmentation and reduce impacts. [emphasis added]