Minimizing bird collisions: What works for
the birds and what works for the utility?
John M. Bridges, Theodore R. Anderson, Dirk Shulund, Linda
Spiegel, and Tim Chervick
Bird collisions with overhead wires have been reported in the United States at least since 1876. A number of
solutions have been tried all with varying degrees of success. Raptor silhouettes, different color marker balls,
“bird diverters”, “flappers” and various other devices to warn birds all work to some degree. However,
depending on the target species and the object being marked, if you use the wrong type or color of device it
may not be effective, could result in a maintenance problem, or may even cause lines to go down. To date,
there is very little published empirical data on which device works for which species or group of species.
Anecdotal information suggests that some things do not work as well for some bird species as they do for
others. This paper will discuss the mitigative measures found in the literature and provide a brief evaluation
of their effectiveness and some of the problems they may create. It will also discuss some of the on-going
research, including the effects of motion and light, where information is available. Evaluation of marking
devices will be based on existing literature, the experience of line crews and personal experience.
Keywords: Bird collisions, power lines, line marking devices, bird diverters, flappers
INTRODUCTION
Bird collisions with overhead wires are a global issue. They have been noted as a cause of mortality in the United States at
least since 1876 (Coues 1876). Avery (1978) summarized the issue of bird collisions with transmission lines for the U.S.
Fish and Wildlife Service. Faanes (1987) examined bird flight behavior in the presence of transmission lines in the northern
Great Plains of the U.S.; Telfer, et al. (1987) discussed bird collisions in Hawaii; Ledger, et al. (1993) discussed collisions
in South Africa; Bevanger (1993) compared ptarmigan (Lagopus lagopus) collision mortality with hunting mortality in
Norway; Boyd (1961) reported on collisions of banded waterfowl in Great Britain; Alonso et al (1993) and Roig and
Navazo (1997) describe collisions in Spain; Hess (1999) is working on the problem in Australia; and De La Zerda and
Rosselli (2002) describe some of the problems in Columbia. Additionally, there are numerous articles dealing with bird
collisions in both peer reviewed journals and the popular press (see California Energy Commission 1995 and 2002). Bird
mortality due to collisions with a single transmission line, is not generally considered not biologically significant (Fannes
1987, and Hugie et al. 1993). However, as Brown (1993) pointed out, cumulatively, bird deaths due to collisions, combined
with other forms of mortality (e.g. habitat loss and fragmentation) can result in significant effects to a population.
Additionally, some lines, such as those crossing wildlife refuges, may have more significant impacts than currently
understood due to inadequate survey efforts.
Birds collide with transmission lines because of hampered visibility or because they are occupied by something else
such as courtship, hunting, or escape. Decreased visibility due to inclement weather can result in a higher incidence of collisions
(Krapu 1974). Incidence of collisions tend to increase during spring mating season and again during the late summer and fall
when young of the year are learning the intricate maneuvers of flight (Hugie et al. 1993). Panic flushes also result in collisions,
particularly of flocking birds (e.g. waterfowl, wading birds, or shorebirds) (Krapu 1974, and Schroeder 1977). Some species are
more susceptible to collisions than other species. Crowder and Rhodes (2002) related this in part to the ratio of wing aspect to
wing loading.
MINIMIZING COLLISIONS
The Avian Power Line Interaction Committee has summarized the methods used to reduce collisions (APLIC 1994). These
include careful location of the line when originally routed. If the line is already in place, a two-year, four-season, study is
recommended to determine if a collision problem exists, what the aerial extent of the problem is, what species are involved
and where on the line the collisions occur. Based on the results of the study, the problem may be minimized by removing
the overhead ground wire, if that is where the collisions occur, and when it is appropriate, and/or marking the lines with
some type of device to make them more visible. Marking devices include aviation marker balls, spiral vibration dampers,
air flow spoilers, bird flight diverters of various designs and dimension, and several devices that have movement such as
swinging plates or flappers.
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Obviously the best way to minimize bird collisions with transmission and distribution lines is avoidance of the situation.
That is, in the initial planning stages of a new line, stay away from areas where birds tend to congregate. These include feeding
and loafing areas, the communication flyways between them, as well as migratory staging areas, particularly wetlands and rivers.
Unfortunately, avoidance is not always practical due to engineering, environmental or economical constraints. Although it is
generally impractical if the line is already in place, in some cases problem lines have been relocated.
In the last 20 years, increased efforts have gone into finding the best methods of dealing with existing lines that are
known to have bird collisions. Two international workshops on the subject of birds and the electric utility industry have been
held in the United States since the early 1990’s. Several others have been held in South Africa, the Middle East, and Europe. To
understand how to make an object more visible to birds, we must first understand how a bird views its environment and how it
reacts to that visual input (see Cook 2001). Obviously most birds are dependent on vision for mating and feeding. One has but to
look at the coloration of breeding plumage or the hunting techniques of raptors, vermivores or carrion feeders.
According to Faanes (1987), most bird collisions in his study occurred with the overhead ground wire when the birds
veered up to avoid the conductors. Beaulaurier et al. (1984) found that removing the overhead groundwire or shield wire was
very effective in the Pacific Northwest. However in areas that experience a lot of lightning, this would leave major transmission
systems exposed to numerous outages. Additionally, there are studies that infer the ground wire is not the cause for collision in
every instance (Anderson 1978 and Krapu 1974). Meyer (1978) found marking the overhead groundwire works with varying
degrees of success. APLIC (1994) lists the effectiveness of various line marking devices (i.e., 12-inch marker balls, spiral
vibration dampers and bird flight diverters) with a range of 40 to 89 percent, depending on device and spacing on the lines.
Brown and Drewien (1995) studied the effectiveness of different marking devices (i.e., swinging plates and spiral vibration
dampers) and they found the marking devices resulted in changed flight behaviors and reduced collisions (by 63 percent and 61
percent, respectively). However they reported the effectiveness varied by device, season and species. The swinging plate had
some initial problems with the clamp. The clamp moved slightly in strong winds and began to wear on the wires. Crowder (2000)
reviewed the relative effectiveness of bird flight diverters and swan flight diverters. He reported that bright colored (yellow) bird
flight diverters were better at reducing collisions than gray (76 percent to 58 percent) but the gray swan flight diverters were
more effective than yellow (44 percent to 25 percent). Roig and Navazo (1997) found that “white spirals” spaced every 10 meters
on the overhead ground wire were effective. Where overhead ground wires were not present, they attached a 35 centimeter long,
black, neoprene strip to the conductor and that worked almost as well. Koops and de Jong (1981) studied the effectiveness of
“bird flight diverters” in Denmark and found that, depending on the spacing of the diverters on the wires, they reduced bird
collisions by 57 to 89 percent. Telfer (1999) found that bird flight diverters had little effect on shearwater (Puffinus sp.)
collisions, but yellow aviation marker balls with 8-inch black dots worked quite well. Beaulaurier et al. (1984) also used orange
aviation marker balls, fishing floats and yellow streamers, all with some success. Bird flappers, a device that attaches to either the
groundwire or conductor, have been suggested by Miller (1993) and Ledger et al. (1993). Van Rooyen (2003) placed flappers on
lines in South Africa and found them to reduce bird collisions. Janss et al. (1999) found the use of raptor models (i.e. eagles
Aquila sp. and Accipiters) mounted on transmission line structures, to reduce collisions. They found that the models had no effect
on collisions or the potential for collisions.
More recent studies and reports on bird vision have led to the development of devices that work in the wavelength that
birds use and have motion that catches bird’s attention. Birds use motion to detect and hunt for food, and avoid predators. Some
birds have the ability to define and distinguish patterns and objects using only motion information (Dittrich and Lea 2001).
Hawks, penguins and insectivorous birds are strictly dependent on motion cues for detecting prey at great distances. Many bird
species have the ability to see at two peak wavelengths of light (Springsteen, 2003). One peak wavelength, 560 nanometers (nm)
or yellow color, is shared with humans in the visible light range. The other peak wavelength of light, 360 nm wavelength, which
is in the A-band of ultra-violet light, is found in sunlight and is invisible to humans. McGraw (2004) states that color signaling by
birds play an important function in locating and acquiring food, attracting mates, mediating aggressive behavior, and avoiding
predation. The complex retina and sensitive vision of birds surpass those of most animals (Hart 2001). Bird feathers reflect light
within the multilayered arrangement of feather barbs and barbules, causing iridescent effect in some bird feathers. This iridescent
color may function in important signaling within different bird species (McGraw 2004). According to Husband and Shimizu
(2001), birds appear to have excellent color vision which may be based on their having four or five photo pigments, compared to
three in primates. This may explain the success Telfer (1999) had with marking lines with yellow marker balls that he painted
with large black spots. However, as Janss et al. (1999) found when using raptor models to haze birds not all birds interpret a
warning device as a warning. Smaller birds tended to harass the models.
At this time there are several studies underway to test the efficacy of the devices to warn birds of objects in the air. Red
Electrica de Espana is testing devices on some of its lines (Roig 2004). Eskom is also testing the “flapper” on flamingos and blue
crane collisions in South Africa (Van Rooyen and Smallie 2003). They found the flappers reduced flamingo collisions by 82
percent and blue crane collisions by 84 percent. There is also a consortium of partners developing the technology to test line
marking devices and monitor bird activity for projects in North Dakota and California (California Energy Commission 2003).
The Technical Advisory Group for this study includes three agencies in the U.S. Department of Interior, two agencies in the U.S.
Department of Energy, two agencies in the U.S. Department of Agriculture, one agency in the U.S. Department of Commerce
and one in the Department of Defense. There are electric utilities, environmental organizations and interested individuals from
five continents also participating. Several state agencies along with EPRI, Inc. and the Avian Power Line Interaction Committee
are also involved.
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CONCLUSIONS
With all of these techniques, it is important to remember that the purpose of the wire is to aid in the reliable delivery of
electricity. The amount of lightning activity has to be considered before removing the overhead groundwire. Aviation
marker balls and anything else placed on a line, tend to accumulate ice and snow in northern latitudes and at higher
altitudes. As one might expect, the bigger the device the more weight will be added to the line. Ice- and wind-loading
potential need to be evaluated before attaching anything to either the conductors or the groundwires. Design engineers can
answer questions on the ability of the line to bear up under the additional weight of the marking device, especially with the
added weight of ice and/or snow. The same is true for wind loading. Aeolian wind dampers are used on distribution and
sub-transmission lines to minimize the adverse actions of wind (i.e., galloping or slapping). These may be useless if a
device with a large surface area is attached to the line or shield wire. Additionally, the clamp that attaches the device to the
conductor or the shield wire, whether it is an aviation marker ball, spiral bird-flight diverter or flapper may also wear on the
wire it is attached to, resulting in failure of the wire. Another engineering issue associated with marking devices is corona
discharge, which can result in audio noise, radio or television interference, create safety issues, or impede the flow of
electricity. The California Energy Commission and the Western Area Power Administration are currently funding research
to determine the corona discharge of several marking devices at various voltages. And finally, whatever mitigation is
applied needs to be reviewed periodically to ascertain its effectiveness (no one device will work for every situation) and
determine the need for repair and/or replacement. If that need arises too frequently, the maintenance of the device and of
the line may become too costly, and these costs are passed on to the users.
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BIOGRAPHICAL SKETCH
John M. Bridges
Western Area Power Administration, P.O. Box 281213, Lakewood, CO. 80228, USA. Telephone: 720-962-7255,
Fax:720-962-7263. E-mail:[email protected],
Mr. Bridges is a terrestrial biologist, managing Western’s Avian Protection Program. He also assists the agency with
National Environmental Policy Act document preparation, endangered species consultations, and biological surveys. He
holds BS and MS degrees in Zoology from Eastern Illinois University.
Ted Anderson
Western Area Power Administration, P.O. Box 35800, Billings, MT. 59107, USA. Telephone:406-247-7385,
Fax:406-247-7408, E-mail:[email protected].
Mr. Anderson is an Environmental Specialist for the Western Area Power Administration’s Upper Great Plains Regional
Office. Mr. Anderson has a BS in Biology from North Dakota State University and an MS in Biology from California State
University, Bakersfield. He has worked with the US Government as Wildlife Biologist, and Environmental Specialist, for
nearly 30 years. He is responsible for implementing the National Environmental Policy Act and coordinating cultural
resource and natural resource consultations for all the projects in Western’s Upper Great Plains Region.
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Dirk Shulund
Western Area Power Administration, P.O. Box 35800, Billings, MT. 59107, USA. Telephone:406-247-7402,
Fax:406-247-7408, E-mail:[email protected].
Mr. Shulund is an Environmental Protection Specialist for the Western Area Power Administration’s Upper Great Plains
Regional Office. He has worked for Western for nearly 5 years. He is responsible for implementing the National
Environmental Policy Act and coordinating cultural resource and natural resource consultations for projects in Western’s
Upper Great Plains Region. He holds a BS degree in Environmental Science and is working on a Masters in Environmental
Studies.
Linda Spiegel
California Energy Commission, 1516 Ninth Street, Sacramento, CA 95814, USA Telephone: 916-654- 4703 Email: [email protected]
Linda Spiegel has been working as wildlife biologist for 22 years and for the Energy Commission for 16 years. Her
experience includes assessing biological impacts from energy-related facilities, and conducting or overseeing research to
resolve these impacts. She currently oversees numerous research projects relating to understanding and/or mitigating avian
fatality from electrocution with power poles and collisions with power lines and wind turbines.
Timothy Chervick
Swift Creek Consulting, 152 North Sun Arbor Terrace #2048, Salt Lake City, UT 84116, USA. Telephone: 801981-8102, Fax: 801-981-8132. E-mail: [email protected]
Mr. Chervick is the President of Swift Creek Consulting, Inc., which provides environmental consulting services to the
energy industry in northwest Colorado and northeastern Utah. Mr. Chervick has a BS degree in Wildlife Management and
Conservation from the University of Wyoming in 1973. He has worked in water quality and biology for over 20 years. Mr.
Chervick has been actively involved with raptors for over 35 years and currently holds a U. S. Fish & Wildlife Service
Master Falconry license within the state of Utah. He has invented products for the electric utility industry, including Vernal
Triangle perch guard, which was designed and field-tested in 1995 and has a patent pending for the “firefly flapper” a
device to warn birds of obstructions and to haze birds from electrical equipment.
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CONTACT LIST:
#1. John M. Bridges, A7400
Western Area Power Administration
P.O. Box 281213
Lakewood, CO 80228-8213
(720)962-7255
#2. Ted Anderson, B0400.BL
Western Area Power Administration
P.O. Box 35800
Billings, MT 591070-5800
(406)247-7385
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