Using Incidental Finds to Update Collision Risk Models at Wind Farms

The US Fish and Wildlife Service has developed an eagle collision risk model for predicting fatalities at wind farms. This model combines eagle exposure to turbines with probability of collision with these turbines, with an... [ view full abstract ]

The US Fish and Wildlife Service has developed an eagle collision risk model for predicting fatalities at wind farms. This model combines eagle exposure to turbines with probability of collision with these turbines, with an expansion factor to determine the annual predicted fatalities at a wind facility. This model was developed from studies of eagle interactions with wind farms, using Golden Eagles and wind farms in the Western United States. Although 18 bald eagles (known) have been killed or injured at wind facilities to date, almost all of these have all been discovered through incidental finds, generally by Operations and Maintenance (O&M) personnel. Much of current post-construction monitoring consists of several years of mortality searches by trained biologists, but this effort is not sustained through the life of the project. We present a methodology for using existing personnel at wind facilities so that incidental finds can be used to update the collision probability model for bald eagles. We recommend wind developers determine eagle detection by unit effort by O&M staff. This can be conducted as part of a larger post-construction mortality monitoring plan, so that the probability of detecting dead or injured eagles can be can be calculated from everyday movements of O&M staff. Wind developers must first determine the area visible by O&M staff (likely roads and pads). Trial carcasses can then be placed with variations in distances from road/pad, vegetation, and weather conditions. Once a detection probability is established, incidental finds of eagles can be used to inform fatality estimates. This in turn can be used to update the collision risk portion of the eagle fatality model. These calibrations can easily be done during trial periods of intensive mortality monitoring, and can then serve as a cost-effective measure of monitoring mortalities of large birds at wind facilities for the life of the project.