Action: Bury or isolate power lines to reduce incidental bird mortality
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A single before-and-after trial in Spain showed a dramatic increase in the survival of juvenile Spanish imperial eagles Aquila adalberti following the burial or isolation of power lines.
In 2008, there were an estimated 65 million km of medium- and high-voltage power lines in use across the world, with the network growing at perhaps 5% a year (Jenkins, Smallie, & Diamond 2010). These power lines are a significant threat to many species of birds, with both direct collision mortality and electrocution (from touching multiple wires at once) killing birds. As well as causing potentially unsustainable mortality, these collisions can be economically costly, especially when large-bodied species are involved.
Species are most at risk if they are large and heavy, with poor eyesight and limited manoeuvrability (Jenkins, Smallie, & Diamond 2010), but some relatively small species, such as gamebirds, are also very vulnerable (Bevanger & Brųseth 2001). Appropriate planning of power lines to avoid high-risk areas (such as those between feeding and roosting grounds) and to follow features such as roads may well reduce bird mortalities (Bevanger 1994), but in many cases wires are already in potentially dangerous locations and techniques are needed to mitigate the damage they cause.
Bevanger, K. (1994) Bird interactions with utility structures: collision and electrocution, causes and mitigating measures. Ibis, 136, 412–425.
Bevanger, K. & Brųseth, H. (2001) Bird collisions with power lines–an experiment with ptarmigan (Lagopus spp.). Biological Conservation, 99, 341–346.
Jenkins, A.R., Smallie, J.J. & Diamond, M. (2010) Avian collisions with power lines: a global review of causes and mitigation with a South African perspective. Bird Conservation International, 20, 263–278.
Supporting evidence from individual studies
A before-and-after trial in the wetlands of the Doñana National Park (Ferrer & Hiraldo 1991), Andalusia, Spain, found that six-month survival for radio-marked juvenile Spanish imperial eagles Aquila adalberti increased from 18% of 17 individuals in 1986-7 to 80% of 15 in 1988-9 following the isolation or burial of previously identified dangerous power lines. This study discusses other eagle management techniques, described in ‘Add perches to electricity pylons to reduce electrocution’, ‘Use signs and access restrictions to reduce disturbance at nest sites’, ‘Foster eggs or chicks with wild conspecifics’ and ‘Remove/treat endoparasites’.