Ecological Archives A025-072-A2

Manuela M. P. Huso, Dan Dalthorp, David Dail, and Lisa Madsen. 2015. Estimating wind-turbine-caused bird and bat fatality when zero carcasses are observed. Ecological Applications 25:12131225.

Appendix B. Calculations of overall probability of detection g at Foote Creek Rim (Young et al. 2003).

From June 2001 to June 2002, one-half of all turbines and all the met towers were searched once every 28 day period. Turbines were 0.6 MW, 40 m to nacelle and 42 m diameter of the rotor swept area and all areas within 63 m of each turbine were searched. Hull and Muir (2010) estimate the distances from turbines within which 50, 80, 90, 95 and 99 percent of fatalities are expected to lie for 3 sizes of turbines and 3 sizes of carcasses. Extrapolating their results to apply to the turbines at Foote Creek Rim, we found that a 63 m radius search plot would comprise ≤ 80% of the fatalities. We conservatively estimated 80%, which when combined with the 50% turbine sample corresponds to a searched area expected to comprise 40% of the total fatalities.

Searcher efficiency and carcass persistence trials were not conducted in 2001–2002, so estimates from 1999 and 2000 were used for bird mortality estimates in 2001-2002. Ninety-two percent (135/146; 95% CI: 087, 0.96) of the large birds were detected in searcher efficiency trials (Young et al. 2003; Table 1).

Fifty-seven percent of the 83 persistence trial carcasses remained after 28 days with an average persistence time of 29.45 (95% CI: 25.81, 33.09) and 57% of trial carcasses remaining after 28 days (Young et al. 2003; Table 2). These statistics were used to describe a Weibull distribution with α = 3.80 and β = 32.59 that was used to model persistence time. Assuming a constant arrival, the probability of arriving in the interval and persisting to the next search was 0.90 (95% CI: 0.93, 0.85). These factors combined to result in ghat = 0.335 (95% CI: 0.309, 0.355).

Literature Cited

Hull, C., and S. Muir. 2010. Search areas for monitoring bird and bat carcasses at wind farms using a Monte-Carlo model. Australian Journal of Environmental Management 17:77–87.

Young, D. P., Jr., W. P. Erickson, R. E. Good, M. D. Strickland, and G. D. Johnson. 2003. Avian and bat mortality associated with the initial phase of the Foote Creek Rim windpower project, Carbon County, Wyoming. Pacificorp, Portland, Oregon.

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