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Abstract

In Lincoln County, Washington, USA, greater sage-grouse (Centrocercus urophasianus) and Columbian sharp-tailed grouse (Tympanuchus phasianellus columbianus) are managed as reintroduced and augmented populations, respectively. Predation by raptors and corvids is a concern, particularly where utility poles may provide hunting perches near leks (i.e., breeding areas). Perch deterrents may offer a mitigating strategy if deterrents reduce the frequency or duration of perching. To investigate the effects of various perch deterrents, we deployed deterrents on 5 power poles retained for use in this study when 33 poles were removed from occupied grouse habitat. We rotated deterrents among poles every 15 to 28 days (x = 19.4 days) from November 17, 2011, through November 20, 2012, so that all deterrents occurred multiple times on all poles. We compared perch frequency and duration on 4 pole caps, 3 insulator deterrents, an untreated control cross arm, and 5 cross-arm-length deterrents: Pupi™ cross arms mounted at a 22° angle from horizontal; Birdzoff™ deterrents; an experimental shroud; Power Line Sentry X™ deterrents; and Zena Designs™ minispike deterrents. We collected 862 independent records of perching events. Raptors and corvids perched most often (χ2 = 146.0, P < 0.0001) on untreated cross arms ( = 0.60 perches/day), and insulator deterrents (x = 0.47 perches/day), and perched least often on pole caps with spikes (x = 0.11 perches/day) and Zena Designs mini-spikes (x = 0.10 perches/day). Perching events were shorter on pole caps with spikes and Zena Designs mini-spikes compared to all other treatments (F8,853 = 23.53, P < 0.0001). Prey captures also were significantly less likely from treated cross arms than from the control cross arm (χ2 = 86.5, df = 4, P < 0.0001). Birds attempting to perch on deterrents often flapped their wings broadly where energized conductors would have existed if the poles had not been decommissioned. On energized poles, electrocution would have been possible in this situation. When perch deterrents are used, insulation or isolation of energized equipment also must be installed to minimize electrocution risk.

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