In the United States, as proposed wind power development sites are evaluated for their viability, one issue that is often considered is the potential impact on resident, migratory, and breeding birds. In order to assess whether birds might be impacted at the proposed Norris Hill Wind Resource Area (NHWRA) of southwestern Montana, preconstruction avian surveys were conducted between August 1995 and August 1996. The researchers learned early on that much of the avian activity was occurring during the night. Marine surveillance radars were therefore used to enhance the collection of data.
This report describes the Before-After Control-Impact (BACI) study design used, with the data presented herein documenting the Before-Impact and Before-Control component for avian use and mortality in and near the proposed wind resource area. Results of the BACI analysis are provided, as well as comparisons of visual and radar detectability. Development has not yet occurred at the site. Should it occur, comparable post-impact data could be collected to complete the study.
The use of marine surveillance radars resulted in the improved detectability of avian movements in and near the NHWRA. The report includes data on use of the NHWRA and vicinity by migratory birds, breeding and local raptors, and breeding and local nonraptorial birds. An assessment of avian mortality is also included. The use of radar lead to the detection of 12 times as many birds as had been detected during previous diurnal visual observations. In addition, radar permitted sampling at night, which was a time of more intense migration.
The research reported in this document was conducted by the authors under a subcontract with the National Wind Technology Center of the National Renewable Energy Laboratory, with funding from the Wind Energy Program at the U.S. Department of Energy.