Remove earth wires to reduce incidental bird mortality
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Overall effectiveness category Likely to be beneficial
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Number of studies: 2
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How is the evidence assessed?
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Effectiveness
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Certainty
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Harms
Study locations
Supporting evidence from individual studies
A controlled before-and-after trial between 1989 and 1995 in boreal and subalpine forests in southern Norway (Bevanger & Broseth 2001) found a 51% decrease in collision mortality of willow grouse Lagopus lagopus and rock ptarmigan L. mutus by a 2.5 km section of 22 kV power line from which the earth wire was removed (49 fatalities before removal, 24 afterwards). There was no corresponding decrease in two control sections (61 vs. 50 fatalities and 20 vs. 27 fatalities). The earth wire was located 1.5 m below the phase conductor lines.
Study and other actions testedA literature review (Jenkins et al. 2010) described a before-and-after trial (Brown et al. 1987) that found an 80% reduction in collision mortality of sandhill cranes Grus canadensis and whooping cranes G. americana following removal of the earth wire from a 3.2 km span of 116 kV line in Colorado, USA.
Additional reference
Brown, W. M., Drewien, R. C. & Bizeau, E. G. (1987) Mortality of cranes and waterfowl from powerline collisions in the San Luis Valley, Colorado. 128–136 Proceedings of the crane workshop, 1985 Platte River Whooping Crane Maintenance Trust, Grand Island, Nebraska.
Study and other actions tested
Where has this evidence come from?
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This Action forms part of the Action Synopsis:
Bird Conservation
Bird Conservation - Published 2013
Bird Synopsis