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Providing evidence to improve practice

Action: Remove earth wires to reduce incidental bird mortality Bird Conservation

Key messages

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A before-and-after study and a literature review describe significant reductions in collision mortalities of cranes Grus spp. and grouse Lagopus spp. following the removal of earth wires.


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.



A 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.

Referenced papers

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2019) Bird Conservation. Pages 141-290 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.