Western EcoSystems Technology, Inc. and Wyoming Wildlife Consultants, LLC initiated a greater sage-grouse radio-telemetry study at an existing wind energy development in southeastern Wyoming in 2009. The University of Wyoming joined this collaborative effort in January 2010, and the National Wind Coordinating Collaborative joined the effort in March 2011. The overall goal of the research was to establish the population-level effects of wind energy development on female sage-grouse seasonal habitat selection and demography. This study represents the only situation in the US where the responses of greater sage-grouse to the infrastructure associated with a wind energy development has been investigated. Our primary objective was to discern the relationship between sage-grouse nest, brood-rearing, and summer habitat selection patterns and survival parameters and the infrastructure of an existing wind energy facility.
The Seven Mile Hill (SMH) study area was located north of Interstate 80 and south of the Shirley Basin in Carbon County, Wyoming, US. A control and treatment area was included in the SMH study area, with boundaries of each of these areas determined from lek locations and radio-marked female sage-grouse distributions. The Seven Mile Hill Wind Energy Facility (SWEF; located in the treatment area) consisted of 79 General Electric 1.5-MW wind turbines and approximately 29 km of access roads. The facility became fully operational in December 2008. In addition to the SWEF, other anthropogenic features present in this portion of the study area included approximately eight km of paved roads and 26 km of overhead transmission lines. The control study area had no wind turbines and was adjacent to the SWEF and south of US Highway 30/287. There were approximately 50 km of paved roads and 17 km of overhead transmission lines in this area. The treatment area had four leks that had an average distance of 1.93 km from the nearest SWEF turbines (range = 0.53 to 4.15 km), while the control group consisted of 6 leks with an average distance of 10.99 km from the nearest SWEF turbine (range = 7.09 to 16.16 km).
We captured and radio-equipped 346 (160 treatment; 186 control) female sage-grouse within an area consisting of a wind energy development and a control area absent of wind energy development in southeastern Wyoming from 2009–2014. We relocated each radio-marked female approximately twice a week during the nesting, brood rearing, and summer periods. We developed a suite of anthropogenic, vegetation, and environmental covariates to estimate habitat selection and survival for all sage-grouse during the nesting, brood rearing, and summer periods. We used a discrete choice habitat selection model to estimate the relative probability of sage-grouse nest site, brood-rearing, and summer habitat selection within both the control and treatment areas during the post-development period. We did not detect a negative impact of the wind energy facility on nest site selection during the study period. Sage-grouse rearing broods generally avoided suitable brood-rearing habitat near anthropogenic infrastructure that includes wind energy development, major paved roads and transmission lines. Although avoidance was consistent across the years of our study, avoidance of wind turbines was more pronounced in 2012-2014 compared to 2009-2011, suggesting a lag period in the ultimate population-level response to the development of a wind energy facility. Although distance to turbine was not strongly associated with summer habitat selection, the percentage of disturbance associated with wind energy infrastructure did appear to influence summer habitat selection.
In addition, we estimated survival during each seasonal period to estimate the effect of the SWEF on population fitness. The SWEF did not have a negative effect on sage-grouse nest survival within the study area over the six-year period, and nest survival did not differ between nests of females captured at treatment and control area leks over the study period. The SWEF did not have a negative effect on sage-grouse brood survival within the study area over the six-year period. Survival was related to habitat features and anthropogenic features that have existed on the landscape for >10 years. Lastly, the SWEF did not have a negative effect on female sage-grouse summer survival within the study area over the six-year period. After controlling for annual and natural variability, we observed a positive effect of the SWEF on female survival when the percentage of disturbance within 0.81 km of a sage-grouse location increased from 0% to 3%.
Our study is the first to estimate the impacts of wind energy development on sage-grouse habitat selection and fitness parameters. Female sage-grouse selection of seasonal habitats was variable relative to the infrastructure associated with wind energy facility, but fitness parameters did not appear to be influenced to a great degree by the infrastructure. This pattern of effect is similar to greater prairie-chicken response to a wind energy facility in Kansas but opposite of sage-grouse response to oil and gas development. Ideally, we would have preconstruction data to identify changes in the population and decipher mechanisms in sage-grouse response to infrastructure; however, we are confident that if such impacts to habitat selection and survival did occur then we would have been able to detect these changes over the 6-year study period.
The lack of other studies investigating impacts from wind energy development to sage-grouse habitat selection and survival limits our ability to make inferences about the cumulative impacts of wind energy development on sage-grouse, but we were able to describe some of the impacts that wind energy developments may have on sage-grouse populations. Although we attempted to account for possible confounding factors, there is the chance that we did not detect important interactions between environmental features and habitat selection and survival patterns.
Future wind energy developments should consider the potential impacts of wind energy development on sage-grouse habitat selection patterns and survival parameters. We recommend facilities similar in size that occupy similar habitats as our study be placed 1.20 km from any occupied sage-grouse nesting, brood-rearing, or summer habitats. We recommend that future research consider predator-prey mechanisms by estimating both avian and mammalian predator densities to better understand the impacts of wind energy development on sage-grouse fitness parameters and to develop appropriate mitigation measures.