Do supplemental perches influence electrocution risk for diurnal raptors?

Abstract

Background: Power lines are amongst the main causes of mortality for birds globally. Electrocution drives the population dynamics of several threatened species of raptors, at local and global scales. Among the many solutions that have been tested to minimize this threat are supplemental perches; however, their efficiency has rarely been assessed. Methods: We designed 43 transects in 4 districts in mainland Portugal to gather data from birds perching on pylons with or without supplemental perches. From 2015 to 2018, transects were surveyed by car at least once. We analyzed the factors driving the use of these supplemental perches, and we analyzed if there were differences in the perceived risk (calculated from measurements and not from field surveys) depending on whether the perching was on pylons with or without supplemental perches. Results: We recorded 548 perches of 14 species. Weather conditions seemed to play a role in birds' choice of pylons with supplemental perches versus pylons without supplemental perches. Models also indicated a strong influence of observational conditions. The use of models showed us an important specific effect in the selection of supplemental perches where available: there are some species with a greater tendency to perch on supplemental perches, even when they use both pylons with and without supplemental perches. For most of the analyzed species and species groups, perceived risk was higher in pylons without supplemental perches compared to pylons with supplemental perches, but there were differences between species. Conclusions: Supplemental perches may be a useful and efficient tool for mitigating raptor electrocution. However, there are many influential factors affecting their success, and their effectiveness with different species groups is not homogeneous. Some studies show higher electrocution rates for certain species and devices and thus, their efficacy must be validated. We propose a two-step validation process, first in controlled conditions and then in the field. A common protocol should be established to enable comparisons between studies.

Wildlife and power lines: guidelines for preventing and mitigating wildlife mortality associated with electricity distribution networks

“…Their effectiveness may be limited if the support provides other attractive but dangerous perches. Some studies show higher electrocution rates for certain species and devices; therefore, their efficacy has to be validated (Sánchez et al, 2020).…”

Birds and plastic pollution: recent advances

“…In addition, as long-lifespan species (e.g., albatrosses, shearwaters, and vultures) can breed over many decades (Moore 2008 ), they could be used to evaluate the potential toxicological effects of chronic plastic exposure on both individual survival and reproductive output (Kramar et al 2019 ; Marín-Gómez et al 2020 ; Sánchez et al 2020 ). Furthermore, these species could be used to evaluate the effects of food contaminated with plastic debris and the intergenerational transfer of MPs through allofeeding of offsprings (Sánchez et al 2020 ), as observed in the Cory’s Shearwater ( Calonectris diomedea ) fledglings (Rodríguez et al 2012 ), Providence Petrel ( Pterodroma solandri ) (Bester et al 2010 ), Black-footed Albatross ( Phoebastria nigripes ) (Rapp et al 2017 ), Laysan Albatross ( P. immutabilis ) (Young et al 2009 ), Short-tailed Shearwater (Carey 2011 ), Wedge-tailed Shearwater ( A. pacifica ) (Verlis et al 2013 ), Flesh-footed Shearwater (Lavers et al 2014 ), and other petrels (Rapp et al 2017 ). Finally, model bird species (chicken and Japanese Quail) could be used to clarify the potential regulatory mechanisms associated with physiology, behavior, and neuroendocrinology upon exposure to different sizes of MPs.…”