Developing an Operations Staff-Based Monitoring Protocol for Eagle Fatalities at Wind Energy Facilities

Fatality monitoring has long been a primary component of post-construction surveys aimed at determining a wind energy facility’s direct impacts on wildlife. Recently, additional emphasis has been placed on identifying... [ view full abstract ]

Fatality monitoring has long been a primary component of post-construction surveys aimed at determining a wind energy facility’s direct impacts on wildlife. Recently, additional emphasis has been placed on identifying impacts on eagle populations specifically, and mitigating those impacts when they occur. As eagle programmatic take permits are issued, permit holders will be required to conduct fatality monitoring to ensure compliance with regulatory requirements. In most cases, two years of fatality monitoring may be needed; however, survey duration may be longer to assess the efficacy of additional conservation measures when implemented. Fatality monitoring can be a substantial expense for a facility, often costing thousands of dollars per turbine each year. Our objective was to develop a more cost-effective yet viable eagle fatality monitoring protocol that can be integrated into the regular maintenance routines of operations personnel at most wind energy facilities. A fatality estimate requires three components: 1) carcass detection rates using systematic carcass searches, 2) experimental data on carcass persistence, and 3) the proportion of carcasses expected to land in searched areas. We measured these parameters at three wind facilities in Washington and one wind facility in California. A preliminary study using feathered turkey decoys placed within 40 meters (m) of turbine bases showed that operations personnel and 3rd party biologists had similar rates of detection (both > 0.80) under these circumstances. Follow-up studies have focused on the decoy detection rates of operations personnel while conducting modified Spill Prevention, Control, and Countermeasure (SPCC) checks; these checks are typically done once a month as a routine maintenance requirement. Modified SPCC checks required operations personnel to scan along roadways and exit the vehicle at each turbine base to scan the surrounding terrain with binoculars. Decoys were placed out to 150 m from turbine bases to provide greater coverage of the anticipated carcass fall area. Detection rates during modified SPCC checks were generally high, with over 80% detection of all decoys placed within 100 m of turbine bases across easy and moderate visibility areas. Large raptor carcass persistence, estimated using an interval-censored modeling approach, varied from 28 to 61 days. We estimate that 95% of large avian carcasses fall within 100 m of turbine bases, while 99% fall within 150 m. Using these estimates, and assuming a 30 day search interval, the overall probability a large avian carcass would be available and detected by operations personnel ranged from 0.50 to 0.69. We feel that these rates offer a viable monitoring method for inclusion in facility Eagle Conservation Plans, therefore eliminating the need for 3rd party eagle fatality monitoring.