Wind turbines effect on avain mortality

To: "birding-aus" <>
Subject: Wind turbines effect on avain mortality
From: "Reid" <>
Date: Fri, 6 Jul 2001 08:22:32 +1000
Following some discussion earlier on this list, I contacted:

Albert M. Manville, II, Ph.D.
Wildlife Biologist: Bird Strike, Policy, & Internatl. Issues
Division of Migratory Bird Management
U.S. Fish & Wildlife Service

who has now forwarded the following from the the Green Energy News from E
Source.  In summary, what this article suggests is that siting of wind
generators must include a detailed study of the bird populations of the
area, both sedentary and migratory, the habitat and bird usage of the area.
Note, howver, that it also appears to be written from the 'wind energy
developers' point of view.

Death From Above?
E Source Opinion
The popular press, general public, and many in the energy industry have
mistakenly concluded that most wind generation sites kill a large number of
birds, including raptors that are considered endangered. In fact, the impact
of wind turbines on bird populations -- an issue euphemistically referred to
as "avian mortality" -- is very limited at every site in the U.S. except
one.  E Source concludes that over time, this will become a non-issue for
wind energy developers and green energy marketers.

Wind energy generation will be increasingly in the public eye as prices for
delivered wind energy fall and more large projects come on line. Last year
the wind industry added 3,800 megawatts (MW) of capacity worldwide -- a 28
percent growth rate. The American Wind Energy Association predicts that some
5,000 MW of new wind generation will come on line in 2001, with strong
growth in U.S. markets.

Wind energy is also viewed very positively by the general public, and that
bodes well for those marketing it at a premium price. E Source regularly
recommends that wind energy should have a prominent role in green energy
products whenever the resource is available.

But every story touting the environmental benefits of wind energy also
includes a note that avian mortality is a concern, and that this negative
must be weighed against the benefits of avoided emissions. This is not
surprising, given that throughout the 1990's the environmental community
itself was divided in its support of wind energy because of avian mortality
concerns.  Sierra Club literature has called wind towers "the cuisinarts of
the air." And in 1994, the National Audubon Society called for a moratorium
on new wind-farm developments in important bird areas.  Concern about avian
mortality has slowed and even stopped development of several wind generation
projects, putting a halt to projects in Washington State and California as
recently as 1999.

Studying Avian Mortality: A Brief History
In the late 1980s, the California Energy Commission sponsored several
studies on avian mortality at the state's largest wind generation
development in the Altamont Pass Wind Resource Area. One of the studies
conservatively estimated that 39 golden eagles plus 100 to 300 other raptors
were killed each year in the Altamont Pass development. The study generated
considerable press, in part because golden eagles and other raptors that
were being killed are protected by the Endangered Species Act.  As a result,
several more studies were launched, including one in which golden eagles
were tagged and tracked for three years. All of the studies confirmed that
avian mortality in the Altamont Pass development is indeed frequent and

The Altamont research had several very tangible impacts. First, it tainted
the fledgling wind industry by suggesting that wind generation might be no
more environmentally benign than traditional forms of electricity
generation. But on the plus side, it made the wind industry more careful
about researching sites for potential avian mortality issues. It also set in
motion a furious research effort by the federal government and the private
sector designed to document and assess the scope of avian mortality at other
sites, and then develop solutions to limit the phenomenon.

Latest Research and Field Experience
The concerted research effort has yielded an interesting and overwhelming
finding -- avian mortality simply isn't an issue anywhere in the U.S. except
Altamont Pass. A study completed in December 1999 for the National Wind
Coordinating Committee said, "Of the numerous commercial sites in operation
today in the United States, bird fatalities have been identified only at the
Altamont Pass development." This conclusion is based on separate research
projects done at wind generation facilities in New York, Pennsylvania,
Vermont, Minnesota, Wisconsin, Oregon, Colorado, and other sites in
California. "Frankly, avian mortality does not play much of a role for me
when considering a wind site," says Dale Osborn, who has developed many
sites over the past 20 years, including several that were specifically
studied. "I always do the required bird assessments just to be careful, but
in the few cases where there has been any question about avian mortality,
I've gotten out of the deal before anyone even knew the land was being
considered for wind generation. In most cases the issue never comes up."

There are a number of potential explanations for the marked difference
between Altamont and other sites. One possibility is that careful study of
bird populations and flight patterns has eliminated potentially dangerous
sites before they were developed. Altamont Pass has one of the highest
concentration of raptors known; the area has a huge population of ground
squirrels and other animals that serve as the main course for eagles and
other raptors. It's also possible that mitigation techniques have had the
desired effect. Certainly, wind turbine manufacturers responded to the avian
mortality issue with a raft of design changes; today's slower-moving turbine
blades pose less of a threat to birds, and newer "tubular towers" are
thought to be less appealing to raptors as roosting or resting spots than
the older lattice structures.

Whatever the reason for the discrepancy between bird kill levels at Altamont
and other wind sites, avian mortality is not nearly as big a problem as many
researchers originally assumed on the basis of data collected only from
Altamont Pass.

More Information
For more information about research into avian mortality, please see the
National Wind Testing Center's Web site at
In addition, there is a very complete library of study results at

Ralph Reid

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