Shrubsteppe historically was the dominant habitat in eastern Washington. The quantity, quality, and configuration of shrubsteppe have been adversely affected by conversion for crop production and hydropower, a differential high loss of deep-soil communities, fragmentation through habitat conversion, roads, power lines, and fences, and alteration of the vegetation through over-grazing, invasion by exotic plants, and changes in fire frequency. Today, less than 40% of the shrubsteppe remains, and much of it is degraded, fragmented, and/or isolated from other similar habitats (Jacobson and Snyder 2000). Shrubsteppe is considered a ‘priority habitat’ within the state of Washington (Washington Department of Fish and Wildlife 2008) that warrants special management considerations due to threats from human-associated causes.
Loss, degradation, and fragmentation of extensive shrubsteppe communities has greatly reduced the habitat available to a wide range of shrubsteppe-associated wildlife including several bird species restricted to this community type (Vander Haegen 2007). Sage sparrows (Amphispiza belli), Brewer’s sparrows (Spizella breweri), sage thrashers (Oreoscoptes montanus), and greater sage-grouse (Centrocercus urophasianus) are considered shrubsteppe obligates and numerous other species are associated primarily with shrubsteppe at a regional scale. In an analysis of birds at risk within the interior Columbia River Basin, most species identified having a high management concern were shrubsteppe species. Moreover, according to the Breeding Bird Survey, half these species have experienced long-term declines in their populations. In Washington, greater sage-grouse, sharp-tailed grouse (Tympanuchus phasianellus), and ferruginous hawk (Buteo regalis) are listed as state threatened, and sage sparrow, sage thrasher, loggerhead shrike (Lanius ludovicianus), and golden eagle (Aquila chrysaetos) are listed as state candidates.
One potential threat to shrubsteppe-associated wildlife and the habitats upon which they depend is wind power generation facilities. Wind-generated electricity is increasingly recognized as an important option for addressing energy needs within the state of Washington. In addition to augmenting energy needs, wind power is considered renewable and is encouraged by law. Because shrubsteppe is often the dominant habitat in areas with the best wind resources, there is potential for conflict between the needs for wind power and the needs for shrubsteppe and shrubsteppe-associated wildlife. This potential conflict can be attributed to the direct footprint of the wind power facility (the amount of shrubsteppe permanently converted) and to the ecological footprint (the amount of actual displacement of shrubsteppe-associated wildlife). Although the mortality effects of wind turbines on wildlife (impact mortality) have been examined, the potential effects on populations are largely un-explored.
The goal of this research is to examine the potential impacts of the proposed Withrow Wind Power Project (WWPP) in shrubsteppe-dominated habitat north of Withrow, Washington. Because the WWPP is scheduled to be built no earlier than the summer of 2012, there is opportunity to obtain pre-treatment data on both the project site and on control sites not slated for development. The project area also has been used for substantial research on shrubsteppe-associated wildlife in the past, thus providing baseline data on wildlife and on the methods used to monitor wildlife.
- Assess the effects of turbines and related infrastructure on occurrence and relative abundance of passerine birds breeding on the study area.
- Assess the effects of turbines and related infrastructure on attendance at leks by greater sage-grouse at points relatively near (4 and 7 km) and far (>10 km) from the project area.
- Assess the effects of turbines and related infrastructure on use of habitats by greater sage-grouse on the study area.
- Thirty species of birds were detected during breeding bird surveys of 199 fixed-radius circles; the Brewer’s sparrow, vesper sparrow, western meadowlark, horned lark, and grasshopper sparrow were detected most frequently.
- The Brewer’s sparrow was the most common with an average of 2.5 birds detected per fixed-radius circle. The abundance of Brewer’s sparrow was further illustrated by the incidental discovery of 37 nests.
- Fecal pellets were detected from 12 species in 2,384 pellet count plots (8 pellet counts for each of 298 points). Pellets of mule deer and cottontail were the most common.
- Greater sage-grouse pellets were detected on 450 of the 2,384 plots (19%).
- Surveys of sage-grouse leks in Douglas County did not detect males on the proposed WWPP site. Five leks were monitored within 10 km of the nearest proposed turbine with an average of about 26 males/lek. Thirteen additional leks, further than 10 km away, averaged 23 males/lek.
All photos unless otherwise indicated are courtesy of Michael A. Schroeder