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Vantage to Pomona Heights Chapter 4 230 kV Transmission Line Project FEIS Environmental Consequences PAGE 4-70 does not indicate what size of transmission line was present in the study area (Beck et al. 2006). In contrast, a study in Nevada on the response of Sage-Grouse to construction of a 345 kV transmission line did not find any collision mortalities of the 240 hens which were outfitted with radio transmitters (Blomberg and Sedinger 2009). Additional incidental discoveries or anecdotal accounts of Sage-Grouse collisions with transmission lines have occurred, including in Douglas County, Washington (Schroeder 2010). RDFs anticipated to be effective at minimizing collision risk are discussed in Section 4.3.3.2. Predation As discussed in Section 4.3.3.2, transmission lines may result in increased predation on Sage-Grouse, particularly from avian predators (corvids and raptors) that may perch and/or nest on transmission line structures. Raven populations have increased dramatically in the west following human alteration of the landscape and may be more abundant near transmission lines (Howe et al. 2014). While specific studies linking transmission lines and predation risk for Sage-Grouse are lacking (Utah Wildlife in Need [UWIN] 2010), raven research indirectly suggests a link between transmission lines and predation on Sage-Grouse. Sage-Grouse nest failure has been positively correlated with raven abundance (Coates and Delehanty 2010) and occupancy (Bui et al. 2010). However, increased predation on Sage- Grouse might occur at some, but not all transmission line sites. A study in Nevada found no difference in Sage-Grouse nest success by distance to transmission line even though raven densities increased dramatically post-construction (Blomberg et al. 2010). Even the relationship between raven abundance and Sage-Grouse nest success may be complicated. The study in Nevada found that, after the ten-year results were calculated, the distance to transmission line was not a significant negative influence on nest survival, pre-fledgling survival, or female survival (Nonne et al. 2013). In southern Wyoming, Dinkins (2013) documented lower Sage-Grouse nest success (22 percent) when ravens were detected within 550 meters of the nest compared with success at nests with no ravens detected nearby (41 percent). Specific RDFs anticipated to be effective at minimizing increased predation are discussed in Section 4.3.3.1. Potential mitigation actions to compensate for residual predation impacts are described in Appendix B-6 - Framework for Development of a Sage-Grouse Compensatory Mitigation Plan. Disturbance From Human Presence and Avoidance of Infrastructure As discussed in Section 4.3.3.2, visual and noise disturbance from human presence and avoidance of infrastructure have potential to impact Sage-Grouse. Sage-Grouse are known to be sensitive to human presence (Connelly et al. 2000) as well as vehicle traffic and noise (Holloran 2005; Dzialak et al. 2012). Lek buffers recommended to protect Sage-Grouse from disturbance and displacement during the breeding season vary in the literature from 0.6 mile to three miles (Connelly et al. 2000; Idaho Sage-Grouse Advisory Committee 2006). Due to heightened concern for Sage-Grouse within Washington, the USFWS recommended this proposed Project avoid disturbance during the breeding season within a four mile buffer of occupied leks. Behavioral avoidance of infrastructure may be an indirect cause of habitat loss if the proposed Project results in Sage-Grouse avoiding existing suitable habitat. It may be difficult to differentiate between behavioral avoidance and other effects that may decrease abundance of Sage-Grouse near project infrastructure such as increased predation, collisions, or habitat degradation. This section discusses effects of behavioral avoidance on Sage-Grouse abundance and lek persistence, in spite of the uncertainty surrounding the mechanism for these effects.