Eagles enter rotor‐swept zones of wind turbines at rates that vary per turbine

McClure, Christopher J. W.; Rolek, Brian W.; Braham, Melissa A.; Miller, Tricia A.; Duerr, Adam E.; McCabe, Jennifer D.; Dunn, Leah; Katzner, Todd E.

doi:10.1002/ece3.7911

Cited by 11 publications

(32 citation statements)

References 30 publications

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“…(2021), and McClure, Rolek, Braham, et al. (2021) for further details regarding the study site and the configuration and programming of the IdentiFlight system.…”

Section: Methodsmentioning

confidence: 99%

Confirmation that eagle fatalities can be reduced by automated curtailment of wind turbines

McClure

Rolek

Dunn

et al. 2022

Ecol Sol and Evidence

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Automated curtailment is potentially a powerful technique to reduce collision mortality of wildlife with wind turbines. Previously, we used a before–after–control–impact framework to demonstrate that eagle fatalities declined after automated curtailment was implemented with the IdentiFlight system at a wind power facility in Wyoming, USA. We received substantial interest and feedback regarding our study and, here, we implement several analytical suggestions and include more recent data that strengthen the inference we draw from our results. The five main analytical suggestions we received were to (1) exclude from analysis data that were collected during the period when automated curtailment was only partially implemented; (2) only analyse data from a single make and model of turbine; (3) evaluate changes in the rate of fatality, instead of the yearly numbers of fatalities that result from fluctuations around that rate; (4) calculate a standard measure determining effects of a treatment in a before–after–control–impact study and (5) examine yearly fluctuations of the fatality rate during the before period. After incorporating these suggestions and including additional data collected since the prior paper was published, our results confirm prior work. We demonstrate that eagle fatalities were reduced by 85% (95% highest density interval = 12%, 100%) after implementation of automated curtailment. Rate of fatalities declined by 2.85 eagles per year (−0.67, 5.70) between before and after periods at the treatment site and increased by 2.26 eagles per year (−1.77, 7.37) at the control site. Overall, the fatality rate declined by 4.91 (−0.27, 11.27) more eagles per year at the treatment site than at the control site. The probability that the fatality rate declined at the treatment site relative to the control site was 0.97. Our re‐analysis strengthens our inference by using more robust analyses and data to support the conclusions of the prior study suggesting that automated curtailment was effective at reducing eagle fatalities at our treatment site. Because of the site‐ and species‐specific nature of our work, future research should examine the efficacy of automated curtailment at other sites, with other species, and under different curtailment regimes.

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“…(2021), and McClure, Rolek, Braham, et al. (2021) for further details regarding the study site and the configuration and programming of the IdentiFlight system.…”

Section: Methodsmentioning

confidence: 99%

Confirmation that eagle fatalities can be reduced by automated curtailment of wind turbines

McClure

Rolek

Dunn

et al. 2022

Ecol Sol and Evidence

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“…The current curtailment prescription at TW applies equally across all turbines (McClure et al . 2021a). Our previous work at TW demonstrated that some turbines were more likely to have eagles enter their rotor‐swept zones than others; therefore, we suggested that curtailment criteria could be tailored for each turbine (McClure et al .…”

Section: Discussionmentioning

confidence: 99%

“…Our previous work at TW demonstrated that some turbines were more likely to have eagles enter their rotor‐swept zones than others; therefore, we suggested that curtailment criteria could be tailored for each turbine (McClure et al . 2021a). In the current study, we also observed variation among turbines (σ C = 0.35; Table 2) in entry probability into the rotor‐swept zone at TW.…”

Section: Discussionmentioning

confidence: 99%

“…Our results suggest that basing curtailment decisions on altitude and distance is well founded. Beyond 150 m from a given turbine, the curtailment criterion is currently a time to collision threshold where curtailment is triggered if the trajectory of an eagle will place it at the turbine within 10 s (McClure et al 2021a). This criterion might be reconsidered given that fast moving eagles are unlikely to enter rotor-swept zones.…”

Section: Entry Into the Rotor-swept Zone And Curtailment Decisionsmentioning

confidence: 99%

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Flight characteristics forecast entry by eagles into rotor‐swept zones of wind turbines

Rolek

Braham²,

Miller

et al. 2022

Ibis

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Operators of wind power facilities can mitigate wildlife mortality by slowing or stopping wind turbines (hereafter 'curtail') when birds are at an increased risk of collision. Some facility operators curtail when individual birds have flight characteristics (e.g. altitude, distance or relative bearing of a bird's flight path) that exceed some threshold value, but thresholds currently in use have not been empirically evaluated. Overly restrictive thresholds can cause turbine curtailment for birds that never enter rotorswept zones, thereby resulting in excess power loss. We evaluated the probability that birds, specifically eagles, entered the rotor-swept zone (hereafter 'entry probability') in response to their flight characteristics. We used an automated monitoring system to classify individuals as eagles or non-eagles and record flight paths of purported eagles at a wind facility in Wyoming, USA. We used logistic regression with occupancy dynamics and a distance-dependent colonization process to model entry probability. As a result, this model allowed entry probability to decrease with horizontal distance to the nearest turbine. The probability of entry varied with distance to the nearest turbine and approached zero when that distance was more than 202 m. Entry probability peaked when eagles flew 89 m above ground, corresponding to hub heights of turbines (80 m), and decreased to near-zero at altitudes of 189 m or more. Entry probabilities were greatest when flight paths were near the rotor-swept zone and when eagles flew slowly toward the nearest turbine. Compass bearing of a flight path was not associated with entry probability. Our model accurately forecasted entry probability in Wyoming (area under the curve (AUC) = 0.96) and was transferable to another facility in California, USA (AUC = 0.97); therefore, our results may be applicable across a variety of settings. Curtailment criteria can be based on flight path characteristics to forecast entry into rotor-swept zones. The use of distance and altitude thresholds when making curtailment decisions is justified. However, this analysis suggests alteration of the time to collision threshold, with curtailment initiated at greater distances as the speed of the bird decreases. Our novel modelling method and our results can inform curtailment criteria in any situation where curtailment decisions are made in real-time.

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“…Site-specific factors also influence a bird's risk of collision within a wind power facility (de Lucas et al, 2008). Indeed, certain turbines present more collision risk than others (McClure et al, 2021b), even under low bird densities (de Lucas et al, 2012). Weak relationships between pre-construction abundance and post-construction mortality at wind power facilities make it difficult to predict where collision risk will be greatest (Ferrer et al, 2012).…”

Section: Discussionmentioning

confidence: 99%

Flight Altitudes of Raptors in Southern Africa Highlight Vulnerability of Threatened Species to Wind Turbines

et al. 2021

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Energy infrastructure, particularly for wind power, is rapidly expanding in Africa, creating the potential for conflict with at-risk wildlife populations. Raptor populations are especially susceptible to negative impacts of fatalities from wind energy because individuals tend to be long-lived and reproduce slowly. A major determinant of risk of collision between flying birds and wind turbines is the altitude above ground at which a bird flies. We examine 18,710 observations of flying raptors recorded in southern Africa and we evaluate, for 49 species, the frequency with which they were observed to fly at the general height of a wind turbine rotor-swept zone (50–150 m). Threatened species, especially vultures, were more likely to be observed at turbine height than were other species, suggesting that these raptors are most likely to be affected by wind power development across southern Africa. Our results highlight that threatened raptor species, particularly vultures, might be especially impacted by expanded wind energy infrastructure across southern Africa.

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Eagles enter rotor‐swept zones of wind turbines at rates that vary per turbine

Cited by 11 publications

References 30 publications

Confirmation that eagle fatalities can be reduced by automated curtailment of wind turbines

Confirmation that eagle fatalities can be reduced by automated curtailment of wind turbines

Flight characteristics forecast entry by eagles into rotor‐swept zones of wind turbines

Flight Altitudes of Raptors in Southern Africa Highlight Vulnerability of Threatened Species to Wind Turbines

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