Greater Sage-Grouse Habitat Use and Population Demographics at the Simpson Ridge Wind Resource Area, Carbon County, Wyoming

Abstract

EDP Renewables (formerly Horizon Wind Energy) has proposed a wind-energy facility in Carbon County, Wyoming. The Simpson Ridge Wind Resource Area (SRWRA) provides habitat for greater sage-grouse, a federal candidate species considered warranted but precluded for listing under the Endangered Species Act. The objectives of this study included 1) Evaluate and determine the functionality and viability of greater sage-grouse habitat within the influence of the proposed Simpson Ridge wind energy development project; and 2) Determine the population impacts of the wind energy project on greater sage-grouse within the influence of the project.This study was conducted in an area with two proposed wind energy facilities and one existing wind-energy facility. Our general approach was to compare greater sage-grouse habitat selection and demographics on proposed wind energy development areas pre versus postconstruction of the wind energy facilities to determine if wind-energy facilities influence grouse distributions or population growth. The first two years of study were designed to collect data on greater sage-grouse populations in and near the SRWRA necessary to determine pre-treatment seasonally selected habitats (e.g., nesting areas, brood-rearing areas, lek visitation, summer habitat, and winter habitat) and population-level vital rates (e.g., productivity and survival). The presence of an existing wind energy facility in the project area allowed us to obtain some information on initial sage-grouse response to wind turbines the first two years following construction. To our knowledge these are the first quantitative data on sage-grouse response to an existing wind energy development. The purpose of this report is to present results of the first two full years of data collected from April 1, 2009 through March 30, 2011. This study was selected for continued funding by the National Wind Coordinating Collaborative Sage-Grouse Collaborative (NWCC-SGC) and has been ongoing since March 30, 2011; however, the focus of the study switched from collecting pre-construction data for the SRWRA to collecting post-construction data for the existing 79-turbine PacifiCorp Seven Mile Hill wind energy facility. Future reports summarizing results of this research will be distributed through the NWCC-SGC.The SRWRA encompasses 28,600.92 acres in Carbon County, Wyoming, between the towns of Hanna and Medicine Bow, and south of US Highway 30. The SRWRA contains numerous ridges interspersed with rolling to hilly plains. Elevations range from 6,700-7,840 feet above sea level. The SRWRA is situated near the base of the Snowy Range Mountains to the south, and lies south of the Shirley Basin. Climate is classified as a semiarid, cold desert with mean annual precipitation of 12 inches (30.5 centimeters [cm]). The SRWRA is almost entirely (96.7%) comprised of scrub-shrub, with the dominant shrub being Wyoming big sagebrush. Grassland composes an additional 1.9% of the study area. All other habitat types each compose less than 1% of the area individual...