BulkTransmission/Migratory Birds

From Open Energy Information

Transmission Migratory Birds

Migratory Birds
Present, Potentially Affected

The Migratory Bird Treaty of 1918 provides regulations to protect birds from human impacts. It prohibits activities that: “Pursue, hunt, take, capture, kill, attempt to take, capture or kill, possess, offer for sale, sell, offer to purchase, purchase, deliver for shipment, ship, cause to be shipped, deliver for transportation, transport, cause to be transported, carry, or cause to be carried by any means whatever, receive for shipment, transportation or carriage, or export, at any time, or in any manner, any migratory bird, included in the terms of this Convention . . . for the protection of migratory birds . . . or any part, nest, or egg of any such bird." (16 U.S.C. 703). This treaty applies to the United States of America and its territories.

Examples of listed birds are the following:

  • Bald eagle (Haliaeetus leucocephalus)
  • Black-capped chickadee (Parus atricapillus)
  • Common night hawk (Chordeiles minor)
  • Red tailed hawk (Buteo jamaicensis)
  • Barn owl (Tyto alba)
  • Snowy egret (Egretta thula)

Migratory Birds Impacts & Mitigation

Infrastructure such as transmission line towers, power lines, ancillary facilities, and substations harm migratory birds, as they are not accustomed to coexisting with high voltage and pathway obstruction. The nesting season lasts from May 1st-September 15th, activating special provisions to protect birds. If construction activities occur during these months, young bird development becomes threatened.

The following mitigation measures can decrease the impacts to birds and transmission line facilities:


  • Provide training programs for employees to learn bird migration patterns, area specific species, essential habitats, and laws protecting birds. Develop an Avian Protection Plan to take proactive measures against bird electrocution and injury.

Avian Protection

  • To mitigate avian collisions with transmission lines, mark shield wires, guy wires, and overhead optical ground wires with flight diverters. Conduct similar processes in areas where the line crosses, or is adjacent to water.
  • Close off any gaps or narrow open hollow spaces in the proposed facilities or structures capable of trapping cavity-nesting birds. Fill or cap any open-ended posts to discourage new nests during construction.
  • Cover phase conductors with manufactured covers, add perch discouragers on cross arms and on top of poles and space each conductor farther than the minimum distance required to mitigate avian electrocution. Furthermore, use longer horizontal insulators, suspend phase conductors on top of poles and cross arms, install horizontal jumper support to increase the phase-to-ground separation, replace tension members with fiberglass or non-conducting materials, cover tension members with dielectric material, use fiberglass poles or switches, and install standard nest discouragers.

Nest Monitoring

  • Hire a biologist to conduct pre-construction surveys that determine active bird nest status (i.e., containing eggs or young, or a mated pair is observed exhibiting territorial defense, carrying nesting material, and/or transporting food). In some situations, biologists allow vegetation clearing near active bird nests, however noise and physical barriers are mitigation measures to further protect the young birds until they have either “fledged or failed”. In other situations, construction restraints, area closures and site relocation may be suggested to protect the bird habitat.
  • Typical surveys occur within 500 feet of tower sites, laydown/staging areas, substation sites, access/spur road locations, or any other area subject to ground disturbance. If no nests are found, proceed with construction.