Refining estimates of bird collision and electrocution mortality at power lines in the United States.

Scott R Loss,Tom Will,Peter P Marra,Antoni Margalida

doi:10.1371/journal.pone.0101565

Abstract

Collisions and electrocutions at power lines are thought to kill large numbers of birds in the United States annually. However, existing estimates of mortality are either speculative (for electrocution) or based on extrapolation of results from one study to all U.S. power lines (for collision). Because national-scale estimates of mortality and comparisons among threats are likely to be used for prioritizing policy and management strategies and for identifying major research needs, these estimates should be based on systematic and transparent assessment of rigorously collected data. We conducted a quantitative review that incorporated data from 14 studies meeting our inclusion criteria to estimate that between 12 and 64 million birds are killed each year at U.S. power lines, with between 8 and 57 million birds killed by collision and between 0.9 and 11.6 million birds killed by electrocution. Sensitivity analyses indicate that the majority of uncertainty in our estimates arises from variation in mortality rates across studies; this variation is due in part to the small sample of rigorously conducted studies that can be used to estimate mortality. Little information is available to quantify species-specific vulnerability to mortality at power lines; the available literature over-represents particular bird groups and habitats, and most studies only sample and present data for one or a few species. Furthermore, additional research is needed to clarify whether, to what degree, and in what regions populations of different bird species are affected by power line-related mortality. Nonetheless, our data-driven analysis suggests that the amount of bird mortality at U.S. power lines is substantial and that conservation management and policy is necessary to reduce this mortality.

Highlights

Collisions and electrocutions of birds at power lines have long represented a major conservation issue [1,2], and the current proliferation of electrical infrastructure is increasing this threat [3]
We used the search terms: ‘‘bird electrocution,’’ ‘‘bird wire collision,’’ and ‘‘bird power line collision,’’ and the previous terms with ‘‘bird’’ replaced by ‘‘avian.’’ We used: ‘‘United States length of electrical lines’’ and ‘‘United States number of electrical poles’’ and the previous two terms with ‘‘electrical’’ replaced by ‘‘power,’’ ‘‘distribution,’’ and ‘‘transmission;’’ ‘‘line’’ replaced by ‘‘wire;’’ and ‘‘pole’’ replaced by ‘‘pylon’’ and ‘‘tower.’’ We checked reference lists to locate additional sources, and we contacted three experts in the field to inquire if they knew of additional unpublished studies
Our annual estimates of between 8 and 57 million birds killed by collision and between 0.9 and 11.6 million birds killed by electrocution indicate that bird mortality at U.S power lines constitutes a major source of anthropogenic mortality

Summary

Introduction

Collisions and electrocutions of birds at power lines have long represented a major conservation issue [1,2], and the current proliferation of electrical infrastructure is increasing this threat [3]. Between 10 and 41 million birds are likely killed each year by power line collisions in Canada [5]. In the United States, rough estimates of annual mortality range from hundreds of thousands to 175 million collisions [6,7] and from tens to hundreds of thousands of electrocutions [7]. This amount of mortality would rank power lines above other structures that kill birds, including wind turbines and communication towers [8,9]. Mortality at power lines may contribute to population declines for some species, as evidenced by studies documenting that power line-caused mortality can cause a large percentage of total mortality for species from several avian orders [10,11,12,13,14]

Methods

Results

Discussion

Conclusion