by Dave Stone

As long ago as the 1880s birds have been dying in collisions with tall, lit structures. Currently there are more than 75,000 radio, TV, microwave and cell phone towers in the U.S., with more going up every day to serve the explosion in cell phone use.

Especially hard hit are the nearly 350 species of Neotropical migratory songbirds that breed in North America, in particular, thrushes, vireos and warblers. When migrating at night through mist and fog they are vulnerable to collisions with towers. Conservative estimates place the number of tower-related bird kills at four to five million per year. On one night in 1963, Dr. Charles Kemper collected over 12,000 birds killed in collisions with towers.

Although research is still underway, findings indicate that bird-tower collisions are related to lighting. Birds' eyes are particularly sensitive to the red and infrared spectra of light. Apparently birds are attracted to the red, blinking lights required by the Federal Aviation Administration (FAA) on towers taller than 199'. White flashing lights seem to be less attractive to birds. Red light has been shown to disrupt the avian magnetic compass. However, it is apparently the duration of blinking that has the greatest attraction to birds on foggy, misty nights. The longer the light stays off, the less likely is the attraction.

Very tall towers with numerous guy wires are especially hard on birds. On a foggy night when celestial clues are obscured, the migrating birds are attracted to and confused by tower lights. They fly around and around towers, striking the towers, their supporting guy wires and other birds, often with fatal results.

These fatalities could be considered takings under the Migratory Bird Treaty Act. Unfortunately, the Telecommunications Act of 1996 requires that all television stations be digitized by 2003, which could add up to 1,000 new megatowers (towers over 1,000' in height) to the landscape.

In an effort to minimize the impact on migrating birds, the US Fish and Wildlife Service has developed a set of recommendations for construction and placement of new towers:

1. Install new communications equipment on existing towers. Up to 120 facilities can be mounted on a single tower.
2. Build shorter towers (less than 200') where the FAA doesn't require lighting and use construction that does not require guy wires.
3. For taller towers, use the minimum lighting compliant with FAA regulations.
4. Locate towers within existing "antenna farms" and away from migratory routes, wetlands and other areas where birds congregate.
5. Design towers with the smallest possible footprint and construct them outside of birds' breeding season.