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Issue Brief from the Ornithological Council

Volume 1
Number 8
October 1999

DEADLY SPIRES IN THE NIGHT: The impact of  communications towers on migratory birds

Introduction

Most bird species in North America  migrate at night, and some of these birds are killed when they collide with communications towers. Collisions are more likely with towers of 200 feet or more ("tall towers"), which are required to have lights so pilots can see the towers. Under conditions of low visibility, due to fog or dense clouds, birds seem to be attracted to the lights and collide with the tower or the dozens of guy wires often found on tall towers. Massive mortality, including the death of more than 1,000 birds on a single night at a single tower, has been recorded more than three dozen times at towers exceeding 500 ft in height.

The cumulative impact of these collisions on bird populations on a national, regional, or species scale is unknown but probably accounts for at least 2 million deaths annually. Bird-tower collisions have become of concern due to a rapid increase in the construction of telecommunications towers for cellular phones and digital television.

A simple solution to this problem may exist. Research is needed to find solutions. The key organizations are the Federal Aviation Administration (FAA), Federal Communications Commission (FCC), the U.S. Fish and Wildlife Service (FWS) and the private companies that build and operate towers. Joint funding is probably necessary for this research, which will also require the cooperation of these agencies and private organizations.

What is known about this problem
As of June 1999, over 40,000 lighted towers and tower farms were registered in the  FAA  database of obstacles in the United States that exceed 200 feet in height. FAA regulations require that towers that stand 200 feet or higher have lights so pilots can avoid them. Taller towers often have guy wires to keep them standing. This combination of lights and guy wires is the source of bird mortality at such towers. On clear nights, birds migrate at altitudes higher than most tower heights. When the cloud ceiling is low, or on foggy nights, birds migrate at  lower altitudes and apparently fly towards the lights on the towers. They strike the guy wires or collide with one another. The current rate of tower construction indicates that numbers of such towers is on course to more than double over the next decade. With more towers, there will be more dead birds.

Of the five long-term studies that have been conducted at single tall towers (800+ ft. high), annual documented mortality ranged from 375 to 3,285 bird carcasses per year (20 year average). About half the birds were found dead over many months rather than at single night catastrophes. In Eau Claire, Wisconsin, 1,000 or more birds have been killed at a single 1,000-ft tower on 24 nights since 1957, and a record 30,000 birds were estimated killed on one night in the mid-1970s.

At the current rate of construction, the number of towers in the United States is likely to double to 80,000 by 2010. The Telecommunications Act of 1996 was designed to facilitate the rapid build-out of a massive telecommunications infrastructure in the United States. The institution of digital television will add even more tall towers to the landscape. Similar expansion is underway in Latin America and Canada. The toll on migratory birds in the Americas from communication towers is likely to increase substantially, but no effort is underway to assess the cumulative impact of towers or to minimize that impact.

In 1998,  the American  Ornithologists' Union, Association of Field Ornithologists, Cooper Ornithological Society and Wilson Ornithological Society approved a joint resolution strongly encouraging the FWS to work with the FAA and the FCC to study the magnitude of the problem, including the preparation of a nationwide, cumulative Environmental Impact Statement. The FCC issues tower construction permits on a case-by-case basis. Possible avian mortality is rarely an issue in the decision-making process.

What further information is needed
It is difficult to devise specific policy solutions or technical mitigation measures because the research is so incomplete at this stage. The research needed to develop prevention measures and appropriate regulations falls into three categories.

1. The full extent of bird mortality caused by telecommunications towers is not known. Large kills are infrequent events that occur at a small number of towers, usually during spring or fall migrations on nights when visibility is poor. There may be more large kills that have not been discovered and recorded. The cumulative impact of occasional kills at many towers needs to be determined.

2. Standardized surveys coordinated across many towers could help determine the magnitude of the problem, and which types of towers and lighting systems are most dangerous. Most studies to date are opportunistic and consider only one tower at a time. Standard research practices used to study avian mortality resulting from collisions with wind turbines and power lines could be adopted for use in studies of avian mortality at telecommunications towers.

3. There is almost no research on the mechanism by which birds are attracted to lighted towers. There may be  "bird-friendly" lighting that could greatly reduce or prevent the mass mortality caused by the current lighting systems which tend to attract or hold birds in the vicinity of the tower.  Certain color lights or strobe rates may cause less attraction than others.

OPPORTUNITIES FOR ACTION:  Coordinated effort by the federal agencies and tower owners. An effort led by the FWS is underway to encourage the federal agencies and private companies that own towers to join together to support research to develop solutions to this problem. Both the electric power industry and the wind power industry have undertaken coordinated, voluntary efforts in cooperation with the FWS to reduce the impact of their operations and equipment on bird populations.  The telecommunications industry could follow these examples.  Current opportunities for action include the following:

• The tower owners could give scientists permission to study bird mortality at their towers

Many tower owners have been very cooperative in allowing researchers to study bird mortality at their towers.  This same cooperation will be needed nationwide in order to gather the data needed to determine the full extent of the problem and to develop solutions.

• The FCC could require tower owners to allow research to be conducted under the towers - this could lead to the collection of sufficient data to prepare a nationwide Environmental Impact Statement and to assess prevention methods.

The FCC issues permits for the construction of telecommunications towers. FCC regulation does not require communications companies to permit research on avian mortality at towers. Researchers need permission from the owners of communications towers to collect dead birds under the towers.  Without this research at a large number of towers across the country, the full extent of the problem cannot be determined and prevention measures cannot be tested. The FCC could require, by regulation or as a condition of  a permit,  that surveys conducted according to protocols established by researchers with recognized expertise, be allowed by the communications companies.

•The FAA could give permission to tower owners to change lighting systems so researchers can compare the effects of different lighting systems

FAA permission is needed to study different kinds of lighting systems on towers.  The FAA requires that towers over 199 ft above average ground level have lighting systems for aviation safety.  To evaluate whether different systems for tower lighting might have less impact on birds, the FAA will have to give permission to researchers to conduct these studies.

• Tower owners could make a concerted effort to co-locate their equipment and place equipment on existing structures such as tall buildings in order to reduce the number of towers.

More towers are built than are needed to fulfill a region's communications needs because companies don't always share their towers or always site antennas on existing structures.  Federal regulation neither mandates the co-location of communication antennas nor requires that communications companies show that there are no existing structures suitable for antenna siting.  Co-location of towers would probably reduce the number of migratory bird deaths.  In 1998, the American  Ornithologists' Union, Association of Field Ornithologists, Cooper Ornithological Society and Wilson Ornithological Society approved a resolution encouraging the communications industry to voluntarily reduce the number of new towers by co-locating new transmitters on existing towers.

•Funding is needed for the research needed to reduce bird mortality at their towers

There are few sources of research funding.  Neither the FCC nor the FAA has funds research of this nature. Although the FWS has responsibility for conserving wild bird populations, it has no funding for the needed research. Biological research needed by the Department of Interior natural resource management agencies, such as the FWS, is conducted by the Biological Resources Division (BRD) of the U.S. Geological Survey.  BRD would need additional funding to conduct this research. Some tower owners have funded monitoring studies at individual towers, but there is no funding source for the comprehensive research program needed to find solutions for this problem.

Why are these birds important?
More than 200 species of birds have been shown to be killed at communications towers in the United States. The most common victims are the colorful songbirds that make long distant flights across international borders each year, to and from the tropics.  These birds consume enormous amounts of insects, help to pollinate plants and distribute seeds, and are critical to the $29.2 billion spent on bird-watching and other wildlife watching activities in the United States each year. Many songbird populations are already under pressure from habitat loss or fragmentation, competition from non-native species, and overuse of pesticides. Avoidance or reduction of the human-related causes of bird mortality, such as collisions with telecommunications towers, may contribute to halting and reversing these declines.

REFERENCES:
Avery, M., P.F. Springer., & J.F. Cassel, 1976. The effects of a tall tower on nocturnal  bird migration - A portable ceilometer study. Auk, 93, 281-291.
Avery, M.L., P.F. Springer, and N.S. Dailey. (1980). Avian mortality at man-made structures: An annotated bibliography (revised from 1978 ed.). U.S. Fish and Wildlife
    Service, Biological Services Program, National Power Plant Team, FWS/OBS-80/54.
Banks, R. C. 1979. Human-related mortality of birds in the United States. U.S. Fish Wildl. Serv. Spec. Sci. Rep.--Wildl. 215, 16 pp.
Cochran, William W. and Richard R. Graber. 1958. Attraction of nocturnal migrants by lights on a television tower. Wilson Bulletin, 70:378-380.
Crawford, R.L 1981.  Bird Casualties at a Leon County, Florida TV Tower: A 25-Year Migration Study.  Bulletin #22 of Tall Timbers Research Station.
Federal Aviation Administration Digital Obstacle File.  23 February 1999.  U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration.
Gauthreaux, S. A., Jr. 1996. Bird Migration: Methodologies and Major Research Trajectories (1945-1995). Condor 98:442-453.
Graber, R. R. 1968. Nocturnal migration in Illinois - Different points of view. Wilson Bulletin, 80, 36-71.
Howard, Wilifred. Bulletin of the Chemung Audubon Society. 1963-1983.
Kemper, C. 1996. A study of bird mortality at a west central Wisconsin TV tower from 1957-1995. Passenger Pigeon 58: 219-235.
Larkin, Ronald P., and Barbara A. Frase. 1988. Circular paths of birds flying near a broadcasting tower in cloud. Journal of Comparative Psychology 102:90-93.
Mayfield, H. F.  1996. Kirtland's Warbler in Winter. Birding 28:34-39.
Nearing, J.D. 1998. Assessment of avian population change using migration casualty data from a television tower in Nashville, Tennessee [MSc thesis]  Mufreesboro,
    (TN): Middle Tennessee University. 43 p.

This publication was reviewed by professional ornithologists and other scientific experts  under the auspices of the Ornithological Council.  You may contact the Council for further information.

Citation: Ornithological Council (1999). Deadly spires in the night: the impact of communications towers on migratory birds. Bird Issue Brief  Vol 1, No.  9, 1st Ed.