Predation risk: a potential mechanism for effects of a wind energy facility on Greater Prairie-Chicken survival

Recent expansion of the wind energy industry has raised concerns about the potential effects of wind energy facilities on prairie grouse. For example, efforts have been made to evaluate indirect effects on prairie grouse survival, but it is also critical to investigate the underlying mechanisms to direct conservation strategies. The objective of this study was to investigate the indirect effects of a wind energy facility on the survival of female Greater Prairie-Chickens (Tympanuchus cupido pinnatus) and on the occupancy of avian and mammalian predators. Between March and July of 2013 and 2014, we investigated spatial variation in predation risk by sampling occupancy of mammalian and avian predators within 10 km of a wind energy facility constructed in 2005 in Brown County, Nebraska, USA. During the same period, we assessed spatial variation in daily survival of radio-marked females within the same area. We found little evidence that probability of site occupancy (Psi) of avian predators was lower near the wind energy facility (within 2 km: Psi = 0.70, 95% CI = 0.22-0.95; beyond 2 km: Psi = 0.93, 95% CI = 0.02-1.00), suggesting that avian predators did not display local-scale avoidance behavior around wind turbines. Mammalian predators were documented at all of our sample locations, but the capture index for all mammals was lower at sample sites near the wind turbines (P = 0.004). Occupancy of coyotes (Canis latrans), the likely main mammalian predator of adult prairie-chickens in the area, did not vary significantly throughout our study site (within 0.5 km of wind energy facility: Psi = 0.65, 95% CI = 0.07-0.98; beyond 0.5 km: Psi = 0.96, 95% CI = 0.04-1.00), although trends were in the direction expected if coyotes were avoiding the wind energy facility. Distance to wind turbine had no effect on daily survival (S-D) of female prairie-chickens (S-D = 0.9948, S-E = 0.0015). The potential for predators to avoid wind energy facilities, and thus affect predation risk, underscores the complexity of planning to address potential impacts of wind energy as variation in predation risk may have consequences for the population viability of a wide range of species at risk from wind energy development.