Mortality Threats
to Birds - Communications Towers
The Problem
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| Northern Harrier killed on the guy
wires of a communications tower. Photo: Hugh Kingery |
The U.S. Fish and Wildlife Service estimates
that between five and 50 million birds are killed in the U.S.
each year after being attracted by the lights on communication
towers, and colliding with the tower’s structure or guy
wires during night migration. Most incidents happen in poor
weather with low cloud during the spring or fall. In at least
one instance, several thousand birds were killed at a single
tower in one night. At least 231 species have been affected,
with neotropical migrants making up a large proportion of all
species killed.
Approximately 80,000 communication towers
in the U.S. are required by the Federal Communications Commission
to be lit, either because they are more than 199 feet tall,
are in the immediate vicinity of an airport, or are situated
along a major highway. More than 7,000 new towers are being
constructed each year to meet the demand for cellular telephone
and digital television networks, and this is expected to continue
increasing in the foreseeable future.
Despite the level of bird mortality associated
with towers, it is likely impossible to prove that these deaths
are affecting overall bird populations given the range of
other threats operating concurrently. Many of the species
affected are abundant and have reproductive ecology designed
to cope with high rates of mortality, especially among juvenile
birds. However, more than 50 of the species recorded in tower
kills are of conservation concern, and any additional mortality
must be considered a potentially serious threat to these species.
The Tennessee Warbler, a species of significant conservation
concern is among the most commonly killed at towers. Despite
a concerted campaign by conservation groups to encourage tower
construction and communication companies to take the threat
to birds seriously, and help fund research on lighting regimes
to minimize tower impacts, progress has been slow.
Conservationists
have now resorted to legal means to resolve the problem including
opposing specific proposed tower construction projects, and
requesting a system-wide Environmental Impact Statement on
all towers.
The Solution
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| Towers. Photo: Mike Parr |
The U. S. Fish and Wildlife Service (FWS)
has issued voluntary guidelines
for tower construction aimed at minimizing bird kills. These
guidelines include: co-locating new antennae on existing towers;
keeping towers below 199 feet; siting towers within existing
tower “farms”, and not close to sensitive bird
habitat; eliminating guy wires; dismantling inactive towers
as soon as possible; using visual markers in areas of raptor
and waterfowl movements (both groups are prone to daytime
collisions with guy wires); shielding security lighting; and
using the minimum number of strobe lights rather than continuous
lights on towers that do require lighting. The FWS guidelines
indicate that red pulsing or continuous red lights attract
birds more readily than white strobe lights. However, no comparison
between red and white strobe lights has yet been made, and
previous studies have indicated that red lights are less attractive
to birds than white. The Federal Aviation Administration announced
in February 2004 that it was releasing a guidance memo recommending
against continuous or pulsing red lights on towers. The Federal
Communication Commission has hired a biologist to coordinate
its response to the tower kill issue. Clearly more research
is needed to identify
lighting colors and patterns that are the least attractive
and confusing to birds. These lighting systems should then
be fitted to all new towers and retro-fitted to existing towers.
Many citizen groups across the country are fighting individual
tower construction projects, primarily because towers can
be an eye-sore. In some cases, bird conservation considerations
have been helpful to these groups. It can be possible to reduce
the visibility of a tower, and reduce its potential impact
on birds at the same time. Disguising towers in existing buildings,
or building them inside forests so that only the antennae
extend above the tree tops are two examples.
What You Can Do
Support conservation groups that are working
to minimize bird deaths at towers. Write to the Federal Communications
Commission to express your concern that they are issuing permits
for communication towers that are killing migratory birds.
Press for a local zoning ordinance to prevent the construction
of towers in your county (see an example of a
model tower ordinance in Brevard County, Florida). Contacting
a local bird club, state Audubon chapter, and the media may
also help build support for your campaign.
More information
Tower Report prepared for ABC, Defenders
of Wildlife, Forest Conservation Council, and the Humane Society:
"The Scientific Basis to Establish
Policy Regulating Communication Towers to Protect Migratory
Birds."
ABC's
Towerkill Report, "Communication Towers: A Deadly Hazard
to Birds".
ABC/Hawk
Mountain petition to the FCC to prevent proposed tower construction.
Fish and Wildlife
Service Voluntary Guidelines on the siting of towers.
Tower
Ordinance for Brevard County, Florida
Towerkill.com
Website.
The
ABC's of Avoiding Collisions at Communication Towers (USFWS
document)
U.S.
Fish and Wildlife Division of Habitat and Resource Conservation
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