How are power lines used to carry energy?
Electricity is created for and delivered to
the consumer in a 3-part process:
1. A power plant generates energy, then…
2. Transmission lines from tall
transmission towers carry high voltage
energy (115-500 kV) over long distances to
a substation, then….
3. Distribution lines from substations to
smaller pole-mounted transformers carry
lower voltage energy (less than 69 kV) to
businesses and houses.
Both transmission and distribution lines
carry enough energy to harm or kill both
people and birds.
Why aren’t birds electrocuted when they
sit on power lines?
Actually, some birds are. Small birds don’t
usually get electrocuted because they fail
to complete a circuit either by touching a
grounded wire or structure, or another
energized wire, so electricity stays in the
line. Larger birds, however- such as the
California Condor, which has a wingspan of
up to 9.5 feet – are more likely to touch a
power line and a ground wire, another
energized wire, or a pole at the same time,
A Fine Line for Birds
A Guide to Bird Collisions at
Power Lines
International
Migratory Bird
Day (IMBD),
held annually
on the second
Saturday in
May, is an
invitation to
celebrate and
support
migratory bird
conservation.
IMBD Information
web - http://birds.fws.gov/imbd
phone - 703 /358-2318
IMBD Materials
web - http://www.BirdDay.org
phone - 1-866/334-3330
April 2005
giving electricity a path to the ground. In
both situations, the birds are electrocuted
and killed, a fuse is blown, power fails, and
everyone is impacted.
Why do birds crash into power lines?
It is generally believed that birds collide
with power lines because the lines are
invisible to them, or because they do not
see the line before it is too late to avoid it.
Birds’ limited ability to judge distance
makes power lines especially difficult to
see, even as they are flying closer to them.
Large birds are especially vulnerable
because they are not always quick enough
to change their direction before it is too
late. Poor weather conditions, such as fog,
rain or snow, as well as darkness may make
the lines even more difficult to see.
What happens when birds collide with
power lines?
Birds can either be killed outright by the
impact, or be injured by contact with
electrical lines, resulting in crippling which
is likely fatal. Electrocutions can also
start wildfires and cause power outages.
An estimated 5-15 percent of all power
outages can be attributed to bird collisions.
with power lines.
What can be done to help prevent power
line collisions?
There are several ways to help make lines
more visible to birds. Marking wires and
conductors with white wire spirals and
black crossed bands in one study reduced
mortality by up to 75 percent. Other
potentially helpful devices include bird
flappers and diverters, such as the Firefly
and the BirdMark, which swivel in the
wind, glow in the dark, and use fluorescent
colors designed specifically for bird vision.
More research needs to be conducted on
these so-called “deterrent devices” to see if
they truly work.
The practice of burying lines underground,
though it eliminates collision risks, creates
other risks to wildlife habitat and human
safety and is often not feasible from
technical and cost perspectives. Yet, at
times when collision risks to sensitive
species are great, placing the line
underground through critical habitat may
be the best option.
Power companies have been voluntarily
taking steps to help, such as insulating
wires to cover exposed connections and
increasing the distance between wires so
that no contact with ground or another
energized wire can be made by the birds.
One example is Tampa Electric, whose
Avian Protection Plan promises to retrofit
equipment to minimize the risk to birds.
Another leader in the electric utility
industry is the Avian Power Line
Interaction Committee (APLIC), formed in
1989 to deal with collisions and
electrocutions nationwide. It was originally
composed of ten utilities nationwide, the
Edison Electric Institute (EEI), the U.S.
Fish and Wildlife Service (USFWS) and the
Audubon Society. Today it includes 29
utilities, EEI, USFWS, and other utilities,
united in efforts to protect avian resources
while enhancing energy delivery.
Websites with more information:
http://www.aplic.org/
(information about coalition dedicated to
protecting birds while enhancing reliable
energy delivery; not much scientific
information, but has good links to
literature)
http://www.culverco.com/sseng/wires/
(very short article about bird safety on
wires; website devoted to explaining
science and safety of electricity and natural
gas)
http://www.pacificpower.net/Article/
Article43391.html
(published by a power company in western
US; good example of voluntary changes by
power company to help birds)
Example technology: BirdMark bird
diverter (P & R Technologies)
