The Importance of Using Peer-Reviewed Science When Making Raptor Management Decisions

In response to Dwyer and Mojica (2022), Donohue (2022) states, “The USFWS should limit its use of the 2014 model [from Dwyer et al. 2014] to determine appropriate compensatory mitigation for eagle take permits and instead work directly with electric utilities interested in providing retrofit poles for mitigation.” We had the same thought. We phrased it as a question and then conducted and published the research described in Dwyer and Mojica (2022) to evaluate our query.

Based on peer-reviewed studies and original research reported in Dwyer and Mojica (2022), we concluded that the best available science does support broad use of the 2014 model for assessing golden eagle Aquila chrysaetos electrocution risk on distribution power poles throughout the western United States. Specifically, data in tables 1 and 2 in Dwyer and Mojica (2022) demonstrate the association of more complex power poles with greater electrocution risk for golden eagles specifically and for raptors generally across Asia, Europe, and North America, (i.e., across the global distribution of the golden eagle). Those complex pole types consistently have larger risk index scores in the 2014 model. Data in tables 3 and 4 in Dwyer and Mojica (2022) indicate a majority of electrocutions of telemetered golden eagles occurred on poles with high-risk scores as indicated by the 2014 model. In separate research led by the U.S. Fish and Wildlife Service (USFWS), Bedrosian et al. (2020), incorporating conclusions about pole complexity identified by the 2014 model, successfully predicted golden eagle electrocution risk based on utility-derived mortality data, power pole density, and eagle breeding density in Wyoming. Based on the consistency across those peer-reviewed publications, we concluded that yes, the 2014 model is useful in predicting electrocution risk for golden eagles throughout the western United States.

In evaluating our finding that the model is broadly useful, we note the statement in Donohue (2022) that, “Approximately 12% of SCE's circuits are classified as transmission (and subtransmission), with voltages 55 kilovolts (kV) and higher. However, they account for 41% of golden eagle electrocutions. . . .” The comprehensive literature review described in Dwyer and Mojica (2022) indicated golden eagle electrocutions occur primarily on distribution voltages. The Avian Power Line Interaction Committee (APLIC 2006, table 5.1) defines distribution voltages as “2.4 kV to 60 kV” and transmission voltages as “60 kV to 700+ kV.” We used the same threshold in Dwyer and Mojica (2022). Thus, per APLIC (2006), the 55-kV structures mentioned in Donohue (2022) would be considered distribution structures in Dwyer and Mojica (2022). Perhaps the golden eagle electrocutions referenced in Donohue (2022) could be parsed into incidents occurring on 55-kV and larger voltages and published in a peer-reviewed journal to help refine understanding electrocution risk, habitat bias, and detection bias on higher voltage structures.

Donohue (2022) stated “The 2022 paper reclassified groups of poles . . . with no explanation.” We believe this comment refers to the portions of our paper under the heading “Google Earth assessment of power poles that electrocuted a satellite-tagged golden eagle.” As explained therein, we consolidated poles into groups due to small sample sizes for electrocutions of telemetered golden eagles. Donohue (2022) also stated “The paper does not show that poles with the highest risk scores would necessarily be the highest risk for golden eagles.” We agree that more complex poles do not necessarily indicate greatest risk for golden eagles across all landscapes. However, we demonstrate that by pairing pole configuration with the habitat variable in the 2014 model, poles in high-quality golden eagle habitat with the greatest risk scores are useful in identifying poles at high risk of electrocuting an eagle.

Donohue (2022) also stated “Each utility could provide historical eagle mortality data . . . to determine the areas of highest potential risk for avian electrocution (Donohue 2022).” There are hundreds of electric utility companies in the golden eagle's range in North America, and many more elsewhere in the species' range, with a huge diversity of protocols for responding to avian electrocutions. Our experience working with electric utilities throughout North America and internationally is that many utilities do not have historical data in sufficient quantity and quality to determine areas and poles of greatest potential electrocution risk. For this reason, we cannot solely rely on utility data to understand golden eagle electrocutions and thus the need for a model. We previously described issues related to limited availability of avian electrocution data in numerous publications specifically because fully considering biases in opportunistically or incidentally collected data is crucial to their interpretation (e.g., Dwyer et al. 2016, 2019, 2020a, 2020b; Bedrosian et al. 2020; Barnes et al. 2022; Mojica et al. 2022; Kolnegari et al., in press).

To our knowledge, no new North American avian electrocution risk models have been published in peer-reviewed scientific literature in the past 8 y. Certainly, there is room for an updated model of electrocution risk, but to date a lack of data precludes such a model. Data referenced in Donohue (2022) could be incorporated with data from other electric utilities throughout the golden eagle's range into such a model and tested with mortality data from telemetry studies. Such an approach would be consistent with recommendations for increasing the transparency and availability of avian data collected by electric utilities to the mutual benefit of birds (survival) and electric utilities (system reliability; Kettel et al. 2022). We welcome any opportunities for future collaborations that would help utilities optimize their electrocution mitigation efforts for the benefit of raptor conservation.