Birds That Go "Bump" in the Night
Most of us are aware of human/wildlife conflicts such as the animal fatalities we see so often along highways. I just read an article from the January 2011 issue of "Birding" magazine, the publication of the American Birding Association, that describes a conflict that may be news to you. The article summarizes results from studies of bird fatalities from collisions with communication towers (cell phone, radio and television towers) and wind turbines. The dramatic increase in cell towers and wind turbines in recent years has focused more attention on the wildlife effects of these structures on the landscape. Bats are also known to die from such collisions or even near-collisions with wind turbines.
The birds most affected (70 to 80 percent of fatalities in the eastern United States) are those that migrate at night, which are mostly songbirds. The birds will collide with communication towers as well as the guy wires that support the towers. The height of a tower and the type of lights on the tower affect the number of bird fatalities. Here are some results of the studies:
• The fatalities were about four times greater at towers taller than 1,000 feet, compared to towers of 380 to 485 feet.
• There were 16 times more fatalities at guyed towers than at unguyed towers of the same height with the same lighting.
• Fatalities were reduced by 50 to 71 percent by replacing steady burning red lights with flashing red or white lights.
Bird fatalities at wind turbines, which lack guy wires, are considerably lower than at the communication towers, regardless of the type of lighting. The average number of wind turbine collision fatalities across the United States is three to four birds per turbine per year. Other studies have shown that wind turbines can have other negative effects on wildlife, unrelated to the collision potential.
The studies provide another example of how development can affect wildlife in unexpected ways. An encouraging result is that merely changing the type of lighting on tall communication towers with guy wires may significantly reduce the threat to migrating birds.