Orange County NC Website
151 <br />Bird Mortality Standards for Telecommunication Towers <br />Within the continental United States scientists have inventoried some 836 migratory bird <br />species. The vast majority (778) of these are non -game species; the balance is legally <br />hunted. Over 350 species are vulnerable to tower collisions, according to United States <br />Fish and Wildlife Department experts. The nature of their vulnerability is presented <br />below in the Issues section. <br />Conservative estimates nationally put annual bird deaths resulting directly from collisions <br />with towers, guy wires, or the ground at four to five million. Migrating birds are also <br />vulnerable to wind generator turbines, overhead power lines, glass windows, oil spills <br />and other pollution sources, aircraft, vehicles, electrocution, predation, pesticides, and a <br />general loss of habitat. <br />To put the four to five million tower kills in perspective and according to Audubon <br />Society estimates, 10,000 to 40,000 birds die annually from collisions with wind turbines, <br />sixty to eighty million collide with motor vehicles, and 98 million died after flying into <br />plate glass windows. <br />Appendix B lists monthly frequency of over 330 bird species, which have been counted <br />in the Orange County area in 2002, as compiled by the Chapel Hill Bird Club. Appendix <br />B illustrates the trends in numbers of nearly 100 of the most common species observed in <br />Orange County from 1999 through 2003. Most of the local bird species are migratory <br />and are susceptible to the effects of telecommunication towers. Some of the more well <br />known bird observation sites include the Bolin Creek Greenway, Cane Creek Reservoir, <br />Dairyland Road, Few's Ford Access in the Eno River State Park, along the Eno River at <br />Pleasant Green Road, Lake Orange, the Mason Farm, and University Lake. <br />Of the 227 species of Neotropical migratory birds listed in documented <br />telecommunication tower bird kills, all but 28 are listed in the Chapel Hill Bird Club's <br />inventory. Species found within Orange County represent 88% of all species <br />documented in the tower kills, and over 97% of the total birds listed. Most of the <br />Neotropical migratory birds of North America migrate through Orange County or are <br />commonly found within the area. <br />Issues. Along major bird migration routes, a single telecommunication tower may <br />account for as many as 3,000 annual migratory songbird deaths, according to recent <br />studies. Documented single bird death events range as high as 12,000 fatalities. If <br />animal scavenging is considered, these figures could be even higher. <br />Three factors influence bird tower mortality. First, lit towers over 200 feet in height <br />attract migrating birds, particularly if the structure uses red strobe warning lights with a <br />short, regular pulsing rate. Secondly, electromagnetic towers emit energy in the <br />microwave spectrum, which may disrupt migrating bird's ability to navigate at night, by <br />creating force fields and resonating with avian magnetite, the bird's internal navigation <br />system. There may be a trade off between lesser tower heights, which increase human <br />exposure to electromagnetic radiation, and greater tower heights, which increase <br />11 <br />