Minimising Mortality in Endangered Raptors Due to Power Lines: The Importance of Spatial Aggregation to Optimize the Application of Mitigation Measures

Abstract

Electrocution by power lines is one of the main causes of non-natural mortality in birds of prey. In an area in central Spain, we surveyed 6304 pylons from 333 power lines to determine electrocution rates, environmental and design factors that may influence electrocution and the efficacy of mitigation measures used to minimise electrocution cases. A total of 952 electrocuted raptors, representing 14 different species, were observed. Electrocuted raptors were concentrated in certain areas and the environmental factors associated with increased electrocution events were: greater numbers of prey animals; greater vegetation cover; and shorter distance to roads. The structural elements associated with electrocutions were shorter strings of insulators, one or more phases over the crossarm, cross-shaped design and pylon function. Of the 952 carcasses found, 148 were eagles, including golden eagle (Aquila chrysaetos), Spanish imperial eagle (Aquila adalberti) and Bonelli's eagle (Aquila fasciata). Electrocuted eagles were clustered in smaller areas than other electrocuted raptors. The factors associated with increased eagle electrocution events were: pylons function, shorter strings of insulators, higher slopes surrounding the pylon, and more numerous potential prey animals. Pylons with increased string of insulators had lower raptor electrocution rates than unimproved pylons, although this technique was unsuccessful for eagles. Pylons with cable insulation showed higher electrocution rates than unimproved pylons, both for raptors and eagles, despite this is the most widely used and recommended mitigation measure in several countries. To optimize the application of mitigation measures, our results recommend the substitution of pin-type insulators to suspended ones and elongating the strings of insulators.

Using risk prediction models and species sensitivity maps for large-scale identification of infrastructure-related wildlife protection areas: The case of bird electrocution

“…Similar results have been found in studies at the pylon scale (Mañosa, 2001;Janss and Ferrer, 2001;Tintó et al, 2010;Guil et al, 2011) and the regional scale (Dwyer et al, 2016). The relationship between landscape composition and electrocution mortality is heavily influenced by the species involved.…”

“…We did not use our electrocution risk model to obtain estimates of electrocution incidence, given the lack of published studies on scavenging removal rate and imperfect search detection biases that would allow us to relate observed electrocution incidences with total mortality (Lehman et al, 2007;Ponce et al, 2010). Additionally, several authors have recommended against making generalizations on mortality rates for large geographical areas (Moleón et al, 2007;Guil et al, 2011). …”

“…Work by researchers, managers, and conservationists during the past few decades has led to an increased understanding of the factors that influence the risk of bird electrocution, such as bird size and behaviour, design and types of materials used in pylons, and the surrounding habitat (Olendorff et al, 1981;Janss andFerrer, 1999, 2001;Mañosa, 2001;APLIC, 2006;Lehman et al, 2007;Tintó et al, 2010;Guil et al, 2011;Dwyer et al, 2014). Identifying and correcting the most dangerous pylons has been shown to reduce the number of electrocution victims (Tintó et al, 2010;López-López et al, 2011;Guil et al, 2011;Chevallier et al, 2015).…”

“…The process of identifying dangerous pylons generally follows a bird hazard assessment based on characterization of individual pylons by modelling technical characteristics and habitat variables, resulting in a pylon-based risk model (Izquierdo et al, 1997;Janss and Ferrer, 2001;Mañosa, 2001;Tintó et al, 2010;Guil et al, 2011;Dwyer et al, 2014). However, applying this selection procedure is impractical on a large spatial scale because of the time and economic resources needed to characterize and potentially modify all existing dangerous pylons.…”

“…Moreover, electrocution risk is determined not only by hazards associated with individual pylons; the exposure to sensitive birds is also important. Thus, the likelihood of electrocution risk is higher when dangerous pylons are located in areas where electrocution-sensitive birds are present (Fernández-García, 1998;Mañosa, 2001;Tintó et al, 2010;Guil et al, 2011;Dwyer et al, 2014Dwyer et al, , 2016.…”