Some wind energy facilities have been granted permission by the U.S. Fish and Wildlife Service to incidentally take a limited number of individuals of an endangered species. Providing evidence that this number has not been exceeded is a post-construction monitoring goal. Simply observing no fatalities may not provide that evidence because a zero count can indicate that either no animals were killed or that perhaps many were killed, but all carcasses were either scavenged or missed in searches. USGS and Oregon State University scientists have updated their “Evidence of Absence” software tool used to estimate the possible number of fatalities when few or even zero carcasses are found. An accompanying user guide describes the underlying statistical models and contains step-by-step instructions that walk users through the calculations and interpretations of results.
Dalthorp, D.H., Huso, M.M., Dail, D., 2017, Evidence of absence (v2.0) software user guide: U.S. Geological Survey Data Series 1055, p. 109, https://doi.org/10.3133/ds1055.