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US Fish & Wildlife Service FieldNotes

Migratory Birds in Missouri Benefit from Upcoming Changes to Tower Lighting

Region 3, December 7, 2012
Communication towers equipped with steady-burning (L-810) lights.
Communication towers equipped with steady-burning (L-810) lights. - Photo Credit: n/a
Locations of the 2,700  communication towers in Missouri equipped with lighting.  Construction of new communication towers has been increasing at an estimated 6-8% anually since development of the cellular telephone.
Locations of the 2,700 communication towers in Missouri equipped with lighting. Construction of new communication towers has been increasing at an estimated 6-8% anually since development of the cellular telephone. - Photo Credit: n/a

Migration is a perilous journey for birds traveling between breeding and wintering grounds, and adding to the challenge of surviving the trip is the presence of lighted communication towers.

Neotropical songbirds, such as warblers, thrushes, vireos, tanagers, sparrows, etc., use stellar and other physical cues for navigation when migrating at night. However, this navigation can be disrupted during periods of inclement weather (i.e., fog, rain, or snow) when a halo of light is created around warning lights on towers. Under these conditions, birds can become disoriented and drawn into the light. Reluctant to leave the light, they continuously circle the tower and eventually collide with each other, the tower, guy wires, or drop from exhaustion. The Service estimates than each year 4-5 million birds are killed by communication towers.

But hope is on the horizon. Following concerns from the Service and other organizations, the Federal Aviation Administration (FAA) initiated a study evaluating the need for steady burning lights on towers. Steady burning lights have been the standard obstruction lighting recommended by the FAA to ensure aviation safety. But these lights also result in significantly more avian mortalities than other lighting systems (e.g., flashing or strobe lights) and have been identified as the primary cause of avian mortalities at communication towers. However, FAA researchers concluded through this study that steady burning lights can actually be flashed, or in some instances omitted altogether, and still provide sufficient visibility to pilots. As a result, the agency is proposing to redefine their standards on obstruction lighting so that steady burning lights will no longer be necessary.

So what does this mean for birds in Missouri? It means that the number of mortalities should be reduced as new towers are built with lights less likely to attract night-migrating birds. Although the FAA has yet to finalize the changes, Columbia Missouri Ecological Services (CMFO) has already been successful in working with cellular telephone companies to ensure that no steady burning lights are used on communication towers. In addition, CMFO plans to encourage companies to rewire lighting configurations at towers known to attract large numbers of neotropical birds during migration. These improvements will add to existing conservation measures by CMFO, such as working with companies to build towers without guy wires (also shown to increase bird mortalities) and building shorter towers in areas known to support large numbers of migratory birds.

Contact Info: Trisha Crabill, 573-234-2132 x 121, trisha_crabill@fws.gov