When: 10:30-11:30 a.m. Friday, May 10
Where: Student Union Simplot A Ballroom
Who: Patrick Kolar, Boise State graduate student
Title: “Impacts of Wind Energy Development on Breeding Buteo Hawks in the Columbia Plateau Ecoregion”
Abstract: Post-construction raptor fatality and nest monitoring is typically conducted at wind energy projects nationwide. However, pre- and post-construction surveys may fail to locate all nesting pairs and impacts from turbines may vary over the breeding season, potentially leading to biased estimates of reproduction and misleading inferences regarding the impacts of wind energy development if methods are not used to account for imperfect detection. To address these potential issues, I used an information-theoretic approach to examine the influence of multiple spatial and temporal variables on reproductive success, post-fledging survival, and the distribution of breeding pairs from three sympatric Buteo species in the Columbia Plateau Ecoregion (CPE). Although the probability of detecting breeding pairs was relatively high (mean = 71 to 90%, SE = 0.09 to 0.05), and sampling units were likely to be re-occupied (mean = 76 to 100%, SE = 0.14 to 0.10), I was not able to locate all nests in the 2010 or 2011 breeding seasons despite multiple surveys for each species. My research indicates the occurrence of breeding pairs was not associated with wind turbines or surrounding habitat types; instead, ferruginous hawks (Buteo regalis) and red-tailed hawks (Buteo jamaicensis) selected areas in relation to the density of nesting substrates. Swainson’s hawks (Buteo swainsoni) were more likely to nest in areas with other breeding pairs, but my results suggest that all three species may have minimized competition through staggered nesting and spatial segregation. Nest survival models predicted that the daily survival rate (DSR) of ferruginous hawk nests decreased as the number of wind turbines within 3.2 km increased (slope coefficient = -0.89, SE = 0.39, 85% CI = -1.47 to -0.30), but I found no effect of turbines on the DSR for red-tailed hawk nests or any additional variables affecting the DSR for Swainson’s hawk nests. None of the 60 radio-marked fledglings died directly as a result of collisions with wind turbines. his is likely due, in part, to the limited size of the natal home range (mean = 2.38 km2, SD = 1.48), and the relatively short duration of the post-fledging period (mean range = 20.75 to 31.60 days, SE = 1.14 to 3.30). However, model-averaged estimates of the DSR differed by species, and predicted distance to the nearest wind turbine (slope coefficient = 1.14, SE = 0.67, 85% CI = 0.19 to 2.10) and a quadratic effect of age best explained the variance in post-fledging survival. Juveniles from nests closer to turbines were more likely to die from predation or starvation just after fledging and prior to initiating natal dispersal compared to those from nests further away. Taken together, these results suggest a greater effect of wind turbines on ferruginous hawk reproduction compared to the other two congeneric species. The causes of this negative association between wind turbines and ferruginous hawks are unknown, but could potentially include collision mortality or indirect impacts such as disturbance or displacement of breeding adults. I recommend that methods for raptor nesting surveys on wind energy projects be standardized to better facilitate the meta-analysis of long-term data and account for imperfect detection of breeding pairs. Future research should focus on the risk of collision mortality to breeding adult raptors and the associated indirect impacts to reproduction. These data will be vital to understanding the consequences of wind turbine impacts to regional populations.