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<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 nomgame 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 />genera] 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 flyingrnto
<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 200.3. Most of the local bird species aie 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
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