Monitoring of Greater Sage-Grouse and other Breeding Birds on the Withrow Wind Power Project Site: Final Report

In 2010 and 2011 we documented the abundance of greater sage-grouse (Centrocercus urophasianus) and other breeding birds in an area proposed for wind power development in Douglas County, Washington State. The original project goal was to document wildlife use of the site before and after wind power development. However, because the construction project did not proceed, this report summarizes the data collected during the planned â€�"pre-construction” phase of the project. We also present the results of some preliminary analyses on wildlife use of the area relative to existing habitat and landscape variation (both natural and anthropogenic) and recommendations for post-construction sampling and analysis. Specific objectives of the research were to assess the effects of wind turbines and related infrastructure on 1) occurrence and relative abundance of passerine birds, 2) attendance at leks by greater sage-grouse, and 3) use of habitats by greater sage-grouse on and near the project area. We detected 8937 individuals of 37 species during breeding bird surveys in 2010â€"2011. The most common bird species documented on point-count bird surveys were Brewer’s sparrow (Spizella breweri), vesper sparrow (Pooecetes gramineus), and western meadowlark (Sturnella neglecta). Modeling in Program Distance indicated that probability of detection for most species was influenced by observer whereas habitat type had little effect on detectability. A total of 15,078 sage-grouse pellets were identified during pellet count surveys. The presence of existing transmission lines was negatively correlated with the distribution of sage-grouse pellets. No male greater sage-grouse were detected on lek counts on the project site (n = 2 leks); 4 leks were monitored within 10 km of the nearest proposed turbine with an average attendance of about 26 males/lek. Point-counts, pellet counts, and lek counts conducted post-construction should provide sufficient data to examine response of breeding birds to wind power construction on this site. Distance sampling should be used for analysis of point count data and models should test for effects of observer and distance on detectability. Distance to transmission lines should be included in models examining effects of wind power projects on use of habitats by greater sage-grouse.