Can a Model of Avian Electrocution from Southern California be Useful in Guiding Power Pole Retrofitting for Golden Eagles Elsewhere?

A previously published model of avian electrocution risk, “the 2014 model,” was developed by comparing power poles that electrocuted birds (electrocution poles; including 21 golden eagle Aquila chrysaetos electrocutions) to poles not known to have electrocuted birds (comparison poles). The 2014 model produces pole-specific risk index scores between 0 and 1. The scores rank relative risk so electric utilities can maximize conservation benefits per dollar spent by focusing retrofitting on poles with greatest risk. Although the 2014 model was created from a study population of birds and poles in southern California, the 2014 model has potential to be used in managing a target population of raptors including golden eagles throughout the western United States. Use beyond southern California is only appropriate if the study population is similar enough to the target population for the 2014 model to predict risk effectively. To evaluate similarity, we examined five sources of evidence. Two were the relative consistency in electrical safety codes for power poles and body sizes of golden eagles in the study and target populations. Three more were consistency in structure-specific factors associated with 1) golden eagle electrocutions in other studies, 2) other avian electrocutions, and 3) previously unreported golden eagle electrocutions. We found that although the study population in the 2014 model included relatively few golden eagles, data were sufficient to create a model that can be applied to a target population throughout the western United States. The model can also be useful in helping determine equivalencies between pole types if utilities seek to compare benefits of retrofitting small numbers of high-risk poles to large numbers of low-risk poles.