Avian Mortality at Communication Towers: A Review of Recent Literature, Research, and Methodology

Kerlinger, Paul

The recent proliferation of communication towers across the United States has sparked arenewed interest in avian mortality that results from collisions of night migrating birds withthese towers. With more than 50,000 lit communication towers greater than 199 feet aboveground level (AGL) existing and thousands more proposed or planned – and perhaps, tens ofthousands more less than 200 feet AGL – the number of obstacles to night migrating and other birds is increasing rapidly (see www.towerkill.com and http://migratorybirds.fws.gov). These towers, used mostly by the wireless telephone, radio, and television industries, range in height from less than 100 feet (31 m) to more than 2,000 feet (615 m). With high definition television (HDTV) on the horizon, some in the communication industry project that 1,000 new 1,000 foot tall (308 m) towers will be erected.Our knowledge regarding tower kills is rudimentary, despite more than 50 years ofhistory documenting the problem (first reported by Aronoff in 1949; for reviews see Avery et al. 1978, 1980; Banks 1979; Hebert et al. 1995; Kerlinger in press; Trapp 1998; and Manville2000). Basically, we know that birds collide with tall towers and that on some occasions –particularly, but not necessarily always, during inclement weather – these towers kill largenumbers of birds. The species impacted most seem to be night migrating songbirds (warblers,thrushes, vireos, tanagers, cuckoos, sparrows, etc.), although smaller numbers of waterfowl,shorebirds, and other species have also been documented. Current estimates of the numbers of birds killed annually by communication towers range between 4 and 10 million(www.towerkill.com).This report is a review of the most recent literature, research, and other efforts tounderstand the avian-communication tower collision issue from 1995 to the present. It wascommissioned by the U. S. Fish and Wildlife Service as part of their new Communication TowerWorking Group (Working Group or CTWG) initiative. The report summarizes the literature, aswell as research that is now in progress and reports that may soon be published. It also identifies the most active researchers working on the towerkill issue. Research topics included in this review are avian fatality studies at communication towers, the role of lighting andelectromagnetic radiation and radio frequencies in avian collisions with communication towers,orientation and navigation behavior of migrants around communication towers, andmethodologies used to study the towerkill problem. In addition, it summarizes recent studiesfrom the wind power industry that are relevant.