Yesterday at about 10:45, Decorah fledgling EWOT was
electrocuted on a high voltage power line roughly ½ mile from the mulch pile
that both fledglings have been spending most of their time on. It was reported
to us late in the afternoon. We collected and examined him, returning to the
site of the electrocution to gather more information once that was done. Here
is what we know.
The line was a 96 Kilovolt transmission line owned by ITC Holdings (http://www.itc-holdings.com/). In
general, electrical delivery can be divided into two types: transmission and
distribution. High-voltage transmission lines carry electricity over long
distances from power plants or grids to substations. The poles or towers are
physically larger and taller than those that support lower-voltage distribution
lines and don’t support anything except electrical lines. Distribution lines carry
electricity from substations to consumers and are supported by what most of us
probably think of as utility or power poles. Utility poles are often made of
wood and, unlike transmission lines, may also carry telephone and cable wires
or support street lights.
ITC is able to detect fluctuations and other anomalies on
their lines. When they sensed an anomaly, they sent a field technician out to investigate.
He found and collected EWOT, and turned him over to the Iowa Department of
Natural Resources. They saw the transmitter and called Bob to let him know that
an eaglet had been electrocuted.
When we first got word of another electrocuted eaglet, we
assumed it had contacted a standard utility pole. According to Refining Estimates of Bird Collision and
Electrocution Mortality at Power Lines in the United States, electrocutions
occur primarily at distribution lines, while collisions occur at both
distribution and transmission lines. That’s certainly been our experience,
since every eagle we’ve picked up has been found at the base of a distribution
line. I pictured a standard wooden utility pole as we glumly drove over for our
field investigation. I was surprised to instead find a high-power line between
a field and a hill. We hiked out and took a look at the scene. We weren’t able
to find scorch or singe marks on the pole or insulators, and the eaglet’s body
was not at the base of the pole, as we’ve seen elsewhere, but under the lines
three to four feet from the pole.
An examination of the eaglet’s body revealed singeing and
burning around his elbow and feet. Electrocution can’t happen unless a bird’s
body creates a circuit between ground and voltage, or different voltage phases,
allowing energy to flow from high to low. Sitting on a wire won’t harm a bird,
since it doesn’t create a circuit. But he closed a circuit with his wing and
one foot, creating the flow that killed him.
In addition to singeing, the eaglet’s wing had extensive
tissue damage and some severing. Although it seemed unlikely, we needed to know
whether the transmitter had somehow created or closed the circuit that led to his
electrocution. A quick look at the transmitter showed no damage, scorching, or
discoloring. We cut the straps and removed it from EWOT’s body. The straps were
intact and there was no scorching, singeing, or burning under the straps or
backpack pad. Finally, we made sure the receiver could detect the transmitter. The
transmitter was functioning normally, so we concluded it hadn’t been part of our
eaglet’s electrocution.
Bob contacted ITC this morning. The biologist he spoke with
told him that they hadn’t seen an electrocution on a high kilovolt line in the
three years he’d worked for ITC. Having said that, they reported the
electrocution to the U.S. Fish and Wildlife Service and the Avian Power Line
Interaction Committee, and they are assessing steps that can be taken to
prevent another electrocution or collision.
What we think
The pole was up to code and we haven’t had any problems at a
transmission line before, so we suspect the electrocution was a terrible accident.
Other electrocutions and near-misses in Decorah involved distribution poles
with wonderful perching spots near the hatchery, where the eagles regularly
hunt, fly, and hang out. The
transmission pole provides a bad perching spot overlooking a poor hunting
ground bordered by trees. Although electrocution was clearly the cause of death,
we suspect that EWOT might have collided with a wire and dropped, contacting
other wires or the pole before dropping to the ground. Death was very quick.
Where do we go from here?
We don’t know whether ITC will install diverters or a
similar non-collision technology over one death. Companies tend to set
priorities based in large part on collisions, electrocutions, and known
migration/movement paths. Reporting is key and we are very glad the company
didn’t choose to sweep the electrocution under the rug.
Bob talked to ITC this morning. If there are any more
deaths, the company will report them to us, the DNR, and the USFWS. Neither D1, D14, or Four have spent any time near
the high voltage line, but if Four or D1 start hanging out, we’ll make ITC and
everyone else aware of it.
Why can’t you build safe perches?
Alliant Energy, the D12 Memorial Group, the Decorah High
School, and Decorah Building supply were able to make the distribution poles at
the hatchery safer through insulation and safe perches. However, we’re not sure
this was a perching problem and we can’t encourage perching on high voltage
transmission lines since they are too dangerous. If protection is installed, it
will probably be in the form of diverters that make it easy for birds,
including eagles, to see the power lines.
What can we do?
Our wonderful fans want to know what they can do to make
power lines safe. A few suggestions:
- · Does your power company have an Avian Protection
Plan? Click here for more information: http://www.aplic.org/APPs.php.
Birds aren’t the only issue, either – my electrical cooperative is upgrading
equipment because of squirrels! Talk to your company and find out what they
have in place.
- · Report electrocuted animals to your power
company and wildlife agency. If your power company shrugs it off, document the
problem and talk to your state’s regulatory agency. It’s my experience that
most utility companies are very responsive to electrocutions. They kill
animals, destroy equipment, can start fires, and are expensive.
- · Learn more about the issue. A few good places to
start:
While we can’t protect transmission lines with safe perches,
most of our electrocutions have been on distribution lines. This seems like a
good time to share the story of the D12 Memorial Group’s work with making
distribution poles safer.
We are really dismayed by the electrocution of another eagle
but believe we can do better in the future. We’ll continue working with power
companies to improve outcomes for birds of prey and we’ll certainly let you
know what happens here. In the meantime, please feel free to share your stories
of improvement and recovery with us.
