Collisions

Bird collisions may occur because of a combination of biological, environmental and electrical design factors.  Such factors include:

• Habitat, weather, time of day, lighting, human activity
• Bird species (body size, flight behavior, distribution and abundance, flocking behavior, age, sex)
• Power line configuration and location

Power lines located between feeding and roosting areas of flocking birds may present an increased collision risk.  This is especially true for lines near rivers, lakes, or wetlands where fog may be common, making lines less visible.  Human activity near lines may flush birds, with startled bird potentially colliding with power lines.  Heavy-bodied, less agile birds, or those within flocks may lack the ability to quickly negotiate obstacles, making them more vulnerable to power line collisions.  Collisions most often occur with the overhead static wire, which may be less visible than energized conductors due to its smaller diameter.  Most bird collisions involve waterfowl, pelicans, and cranes.

Power line spans in collision risk areas may be marked to make the wires more visible to flying birds.  A variety of line marking devices, including hanging markers, coils, and aviation marker balls, are commercially available.  Line markers should be evaluated and approved by company engineers prior to use.

For detailed information on avian collision causes and solutions, see APLIC’s document Mitigating Bird Collisions with Power Lines: The State of the Art in 1994.  To order a copy of this document, contact rloughery@eei.org or sball@eei.org.  An updated edition of this document will be available in 2011.