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A
crash course in tall towers
I don't how
Charles Kemper did it. From 1957 to 1996 he got up most mornings and
walked a search pattern around the base of a 1,000-foot-high television
tower near his home Eau Claire, Wisc.
Though an avid
birder, he kept his eyes on the ground.
In 39 years he
collected and catalogued over 121,000 dead birds. It's impossible to say
how many he missed, or how many were picked up and carried off by owls,
raccoons or other scavengers.
One of the
worst kills he witnessed, and one of the worst ever recorded, happened
early in his study. On Sept. 20, 1957 Kemper woke to find an estimated
20,000 birds dead on the ground, most of them with broken wings, snapped
necks, stoved heads or smashed bills. He found some of them up to 500
feet from the base of the tower, lying in the road, crushed by passing
cars.
There were so
many dead birds, he said, that men from local businesses raked them into
piles as if they were leaves.
If Eau Claire,
Wisc. was the only place this happened, this would just be a sad and
morbid story. Kemper's study is just one of the most thorough and
longest running of them.
Between
1954-79, more than 42,000 dead birds were collected at the base of the
1010-foot WCTV tower in Tallahassee by Herbert Stoddard and the staff of
the nearby Tall Timbers Research Station.
On a single
winter's morning in 1998, between 5,000 and 10,000 Lapland Longspurs
were found dead within a quarter mile radius of the base of a tower in
western Kansas, many of them impaled on frozen wheat stubble.
The exact
mechanics of tower kills — how and why the birds die — is a mystery.
Most of the mortalities are neotropical songbirds, which are
predominantly nocturnal migrants. The collisions happen at night, often
during bad weather, usually two or three hundred yards overhead.
There are
things that are known, though. Most tower kills happen during the
migration. On clear nights there are significantly fewer mortalities,
meaning most birds probably see towers and avoid them in time.
The bulk of
the kills occur on evenings with low cloud cover. Most likely, some
birds simply don't see the obscured towers and slam into them. (Imagine
driving a dark section of highway and suddenly finding a telephone pole
in your lane.)
The greatest
bulk of mortalities, though, occur on overcast nights at towers more
than 200 feet high, which Federal Aviation Administration regulations
require to be lit.
Observers,
using radar, spotlights and sound monitoring devices, have recorded
masses of birds circling the lighted areas of the towers. The theory is
that the birds, denied their stellar navigational clues by the cloud
cover, are attracted by the glow of the lights and are reluctant to move
on to the darker parts of the sky.
In 1958
William Cochran, an engineer at a TV station in Champaign, Ill., and his
friend Ricard S. Graber observed this phenomenon. In an inquisitive
mood, Cochran shut off the lights, and he and Graber were able to
demonstrate something that many had suspected. A few minutes after
shutting off the lights, the birds dispersed.
There are
people who deny that towers kill birds. Of course, there are people who
deny that smoking causes cancer or that Neil Armstrong walked on the
moon.
If you have
your doubts, a good place to start is the American Bird Conservancy's
web page (abcbirds.org). There you'll find a downloadable report
entitled "Communication Towers: A Deadly Hazard to Birds."
The report is
an analysis of 149 documents describing tower kills, with particular
attention paid to the 47 of those documents that provided specific
information about how many birds of which species were killed.
The assessment
of these documents is frank and to the point, noting that the studies
were of varying quality and methodology. Some of the kill reports
included information about tower height, lighting systems, support
structures, weather data and species make-up. Some did not.
Though these
reports don't conform to a common overall protocol, the culmination of
their conclusions is this: communication towers kill birds.
If there is
any bias in the analysis of the data, it's probably that the number of
birds killed in tower collisions every year is underestimated severely,
meaning the number four million, the US Fish and Wildlife Service's
statistic, is highly conservative. The number probably is closer to 10
million.
In 2000 one of
the tower kill deniers was a man named Mark Baker, an employee of
Industrial Communications and Electronics, Inc., a Massachusetts based
company with offices in North Miami. At the time Baker was pushing a
proposed 970-foot tower on Cudjoe Key, saying it should be built because
no study — to his knowledge — proving tower kills had ever been
conducted specifically in the Florida Keys.
The Monroe
County Commission, spurred on by serious local opposition, denied the
project a permit. ICE sued in federal court, lost, and the case is now
on appeal.
Environmentalists, as well as people who simply don't want to live in
the tower's shadow, thought the danger might have passed. But two weeks
ago, acting as ICE's attorney, David Paul Horan started making noises
about how the county should just settle and give ICE what they want. (He
also said that the project had the support of both the Coast Guard and
Monroe County Sheriff's Office, something that both groups later
denied.)
We're just now
starting to understand how vital the Florida Keys are as a flyway for
migrating North American birds. It just seems kind of daft to throw an
object the size of the Eiffel Tower in their way.
— Mark
Hedden is a writer, birding guide and vice-president of the Florida Keys
Audubon Society. He is owner of Bone Island Bird Expeditions and can be
reached at (305) 587-6059, or at heddenkw@aol.com. |
