California Condors and the
Potential for Wind Power
in Monterey County
California Condors and the Potential for Wind Power in Monterey County
A collaborative study with the Ventana Wildlife Society
and Stanford University’s Solar and Wind Energy Project
Authors
Kelly Sorenson, Executive Director, Ventana Wildlife Society
Apollo Yi Qi, GIS Analyst, Stanford University
Eric Stoutenburg, Project Manager, Stanford Solar and Wind Energy Project
October 2009
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Introduction
The purpose of this study is to elucidate broad-scale movement patterns of the endangered California
Condor in Monterey County to contribute to an understanding of the potential risk wind turbines pose,
if constructed. The authors proactively and voluntarily analyzed wind data and California Condor
movement data to determine if any areas in Monterey County have sufficient wind and where condors
generally do not utilize the airspace. The scope of the project was limited to the California Condor and
did not take into account any other issues or potential impacts to other species of wildlife. The data
used was collected from GPS transceivers attached to free-flying condors released in Monterey and San
Benito Counties between July 2003 and September 2008. It was a collaborative effort by the Ventana
Wildlife Society and researchers at Stanford University. The authors’ intent was to assist policy makers
with establishing the wind turbine ordinances for the county so that an environmentally responsible
development of wind power may be encouraged. This study has three sections. Section one describes
the California Condors in Monterey County. Section two explains wind power and the potential for wind
power in Monterey County. Section three presents the methodology and results of the risk assessment.
I. California Condors (Gymnogyps californianus)
Physical Characteristics
The California Condor is North America’s largest landbird with a wingspan of 9.5 feet (2.9 m). Adults
weigh approximately 22 lbs (10 kg) and juveniles weigh 16-20 pounds (7.3-9.1 kg). Juveniles have black
heads and adults have yellow, orange, pink and red colorations on the head and neck, whereas subadults have a mottled black and orange, which is a sort of intermediate plumage. Condors are black
with wing linings on their underside which turn to white triangular patches on each wing by the time
they reach adulthood. Condors have large feet and instead of having sharp talons, typical of raptors,
they have toenails. They are not known to carry objects with their feet. Instead, they have a large crop
that enables the transport of food for later digestion and feeding their young.
Life History
Nesting – Typical nesting involves a cavity in cliffs, rocky areas in chaparral, or in Giant Sequoia
(Sequoiadendron giganteum) and Coast Redwoods (Sequoia sempervirens). Condors nest in
mountainous areas. A single egg is laid between January and April at which time both parents incubate
the eggs. They do very little to alter the nest cavity. Incubation requires approximately 56 days, and the
chick is hatched semi-altricial. Nestlings remain at the nest for approximately 5.5 months before they
take their first flight. After fledging, the juvenile is dependent on its parents for as long as another 7-8
months.
Foraging – Large mammal carcasses are the most common food items eaten by California Condors. Prior
to the arrival of Europeans, condors probably fed upon Tule Elk (Cervus nannodes), Pronghorn Antelope
(Antilocapra americana), and Mule Deer (Odocoileus hemionus) in the interior and whale species and
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other marine mammals on the coast. Historically, condors primarily fed upon domestic livestock and
Mule Deer. Modern populations of condors feed on domestic livestock, deer and elk species, and once
again marine mammals due to the reintroduction of birds to the Big Sur Coast. Small mammals are also
an important part of the condors’ diet primarily for breeding adults because nestlings require smaller
bones to digest for calcium needs (Collins et al. 2000). Koford (1953) documented 24 mammalian
species fed upon by condors.
Roosting – California Condors require cliffs and large trees for roosting. In central California, roosting
sites are often large groves of Coast Redwood, Ponderosa Pine (Pinus ponderosa), and rocky cliffs and
outcrops.
Mortality Factors
Lead poisoning and shooting were thought to be the most important mortality factors in the historic
population although other causes of death were documented (U.S. Fish and Wildlife Service 1996). In
the modern population, the greatest causes of death are lead poisoning, primarily from spent
ammunition (Church et al 2006), and collisions and/or electrocutions with powerlines (Sorenson et al
2001). In California, powerlines are the number one cause of death with lead poisoning a close second
but in Arizona, lead poisoning is the greatest threat. No condors have died as a result of colliding with
wind turbines, although there were no turbines in the range of the historic condor population and very
few in the modern population.
Range and Movement Patterns
The prehistoric population of condors, dating back approximately 100,000 years ranged from present
day New York to Florida in the eastern United States to the Pacific Northwest to the Southwest and into
Mexico and included Monterey County (U.S. Fish and Wildlife Service 1996). The condor survived the
mass extinction of megafauna about 10,000 years ago but its range was greatly reduced to a Pacific
coastal strip from as far north as British Columbia to Baja Mexico. By the 1980’s the condors’ range was
limited to a small, wish-bone shaped area of the Coast, Transverse, and southern Sierra Mountain
Ranges. The last breeding in San Benito and Monterey Counties took place at the beginning of the
1900’s. In the 1980’s the entire population of condors in California was thought to have been familiar
with the entire range. Condors can make long-range flights of 200 km or more (Meretsky and Snyder
1992).
Condors are dependent on foothills and mountainous areas for flight and avoid valley floors, particularly
larger ones. Added for emphasis the California Condor Recovery Plan states, “It is rare for a California
condor to pass directly over the flat, highly agricultural floor of the [San Joaquin] Valley”…”Where flat,
agricultural regions are much less extensive, such as the Cuyama Valley in Santa Barbara and San Luis
Obispo Counties, California condors freely passed high above enroute to foraging grounds”.
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Conservation and Status
In 1982, the population reached its low point of only 22 individuals and extinction was likely so the
remaining birds were captured and taken into captivity. In 1987, the last wild condor was captured and
taken into captivity and for the first time in thousands of years there were no free-flying condors. The
Zoological Society of San Diego was the first to captive breed condors. Today, there are four institutions
breeding the birds, including the aforementioned, the Los Angeles Zoo, the World Center for Birds of
Prey, and the Oregon Zoo. Captive breeding programs have since raised hundreds of birds for release to
the wild. Release programs now are operational in southern and central California and northern
Arizona. The Recovery Plan goals are to have 150 free-flying individuals in each of two geographically
disjunct populations with 15 breeding pairs each as well as another 150 individuals in captivity. In order
for downlisting to Threatened to be considered, the population must exhibit a positive rate of growth.
As of August 31, 2009, there were 355 California condors alive with 181 of these in the wild and 174 in
captivity. In central California, condors have been released to the wild since 1997 in Big Sur by the
Ventana Wildlife Society and since 2003 at Pinnacles National Monument originally through a joint
effort between the National Park Service and Ventana Wildlife Society. The National Park Service now
operates the Pinnacles National Monument site independently. The US Fish and Wildlife Service is the
lead agency of the recovery program involving many governmental and non-governmental organizations
including those listed above and other groups such as the California Fish and Game, the USDA Forest
Service, the Santa Barbara Zoo.
The California Condor is listed as federally and California state endangered. In addition, the condor is a
“fully protected” species in California under state Fish and Game Code 3511. It is unlawful to take any
California Condors although Fish and Game Code and the Endangered Species Act allow take but only in
special circumstances. The U.S. Fish and Wildlife Service can authorize incidental take of condors but
has not done so anywhere within the range of the species and the California Fish and Game does not
have the authority to allow incidental take.
II. Wind Power Potential in Monterey County
The Wind Resource
As residents of the Salinas Valley are well aware, it can be a windy place to live especially in the summer
afternoons. However, for a commercial project to be economically viable, the annual average wind
speed should be at least higher than 16 mph (7 m/s). Smaller projects or residential applications might
work with less wind depending on the use of the electricity. Of course wind is variable and changes both
through the seasons and years. Seasonal variation can have important implications for the economics of
the project. Wind turbine annual power performance is called its capacity factor, which is the percent of
electric power the wind turbine produced during the year from what it could have produced had it
operated at full power the entire year. Capacity factors for most existing wind farms range from 25% up
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to 50%, with most around 35%. The higher the capacity factor, the faster the return on the investment
in the wind turbine.
To check if a wind resource exists in an area in California, one can start with the wind maps on the
California Energy Commission website. These maps use modeled data that is validated with measured
wind speed data from ground instruments and/or satellites to classify areas based on annual average
wind speed. If the map indicates a potentially viable area, wind speeds are almost always measured
with an anemometer tower at the site of interest for at least one year or more to confirm the wind
resource.
Wind Turbines
Using the power of the wind is an old idea. In the United States, wind driven pumps, like the old ones
still seen in the Salinas Valley, dotted agricultural lands and ranches before the widespread
development of electric power in the 20th century replaced them. Those wind-driven pumps were
specially built to provide high torque to operate the water pumps. Today, wind turbines convert wind
power into electric power and feed it into the electric power system.
Commercial designs of wind turbines generally use three modern aerodynamic blades made of
composite materials. Wind blowing past the blade creates a lift and drag force, some of which rotates
the blades. The torque generated by the rotating blades generally passes through a gear box and a shaft
spins an electric generator. In the large commercial wind turbines, the electric generator is usually a
doubly fed induction generator, and within a range can operate similar to the synchronous generators
found in traditional power plants. Smaller wind turbines use simpler variations of an induction
generator. The large wind turbines use the more complicated generator because it improves the quality
of power delivered to the electric power system and this becomes important as some large wind
turbines generate 5 megawatts of power – enough to power over 1000 homes in good wind conditions.
Almost all wind turbines perform similarly. They generally begin spinning and generating electricity
when the wind blows at 7-9 mph (3-4 m/s), produce full power at 34 mph (15 m/s), and they generally
shut off and enter a survival mode when the wind exceeds 56 mph (25 m/s). These three speeds are
called cut-in, rated, and cut-out speed. As the wind speed increases from the cut-in speed, up to its
rated speed, the electric power produced by the generator in the turbine increases approximately
cubically as the power in the wind increases exactly cubically. Between the rated speed and the cut-out
speed, the wind turbine generates maximum power and sheds any excess wind energy by controlling
the blades’ aerodynamic performance. Smaller wind turbines may behave slightly different since their
control systems are often mechanical.
Modern wind turbines are much quieter than older models. The sound of commercial wind turbines is
well documented for each model, and zoning restrictions on the sound levels, measured in decibels,
restrict how close large commercial turbines can be to inhabited buildings. For most projects, a
qualified acoustic engineer assesses the audio impact of the turbines on the nearest neighbors. The
sound from small wind turbines is generally not well documented by manufacturers and as a precaution
should be placed as far from homes and neighbors on the property as possible.
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Wind Power Development
California has over 2,500 MW of wind power installed mostly in the regions circled below in Figure 1 and
was one of the first states to build wind power.
Wind power development usually follows three stages:
•
Resource assessment and project planning: the most important step is identifying and assessing
the wind resource for the exact location a developer proposes to build a wind farm. Generally,
an anemometer tower at least 164 feet (50 meters) tall is constructed to measure and record
the wind speeds for a minimum of one year. This wind data is then combined with long term
data sets from weather models or other measurement stations, such as an airport or National
Weather Service station, to assess if the long term wind climate is good enough for an
economically viable project. In this stage, other important project factors are considered, such
as connection of the wind farm to the electric power system, land requirements, community
acceptance, financing, permitting, and environmental impacts.
•
Construction: the construction of wind turbines is surprisingly quick. Even the largest wind
turbine can be constructed within a few days and connected to the electric power system within
a few weeks after initial testing. In almost all projects, the electric lines are run underground
between wind turbines and connected to the electric power system at a substation.
•
Operation: wind turbines operate themselves automatically with a system of mechanical and
electrical control systems. In large projects, they can also be remotely monitored and
controlled. Wind turbines receive regular maintenance and compared to conventional power
plants are generally more reliable.
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Figure 1 – California Wind Resources with Emphasis Added on Rich Wind Resource Areas and the Area
of Interest in Monterey County
Current commercial wind
power development
Salinas Valley
Wind power projects and the wind turbines used for each project can generally be broken down into
three categories:
•
Commercial utility-scale wind power: these projects generate and sell electricity similar to a
conventional power plant and are usually greater than 50 megawatts (MW). They install dozens
or hundreds of 2 megawatts or greater turbines. An entire industry of wind power developers
and utilities build and manage these projects. In California, these projects are generally in
Techachapi, San Gorgonio Pass, Altamont, or the Sacramento Delta area.
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•
•
Community-scale wind power: these are slightly smaller projects using wind turbines from 100
kilowatts up to 2 or even 3 megawatts. They generally have different ownership structures such
as a town, city, tribe, or cooperative. In the Midwestern United States and Europe, farmers
have often pooled their money to invest in these projects. Sometimes, the electric power
generated is sold for a return on investment and other times, it is consumed on-site to displace
more expensive purchases of electricity from the electric power system.
Small wind power: these projects are usually for homes, farms, or businesses and use turbines
anywhere from 100 Watts to 300 kilowatts. The power generated by the wind turbine is
generally used right on site and may or may not be connected to the electric power system. In
California, a home owner or farmer can enter a net metering program with the utility where
extra electricity put on the electric power system by the wind turbine is credited against times
when the wind does not blow and the owner is using electric power from the grid. This is how
some people have zero energy bills. Wind turbines not connected to the electric power system
often power batteries for boats, remote cabins or stations, and electric water pumps.
Wind power has three primary advantages over conventional power sources such as natural gas:
•
•
•
Free fuel: the electricity prices of wind power do not depend on the volatile price of a fossil fuel.
This means a properly sited wind turbine in a good wind climate reduces the financial risk of
fluctuating and rising electricity prices for consumers. Generally, the price of electricity
generated from a wind turbine is locked in during the project’s construction based on the loans
used to develop it and the power purchase agreement signed with the utility company.
Less pollution: during their operation wind turbines do not emit air pollution harmful to human
health such as sulfur dioxide, and they emit no greenhouse gas emissions such as carbon dioxide
associated with climate change.
No water use: wind turbines do not use any water to generate electricity, which means farmers
do not have to compete with wind power plants for limited water resources in California. In
contrast, nuclear, coal, and natural gas plants consume large amounts of water for steam
generation and cooling, using water that otherwise could support farming.
Wind power development faces several challenges:
•
•
Permitting: large projects can have significant impacts and this generally requires expensive,
involved, and lengthy permitting at all levels of government. The risk and uncertainty of
permitting has derailed many projects. For small wind, permitting at the county level is varied,
with some counties charging nothing, while others charge fees equal to the cost of the wind
turbine itself. This mix of county permitting policies in California has let small wind flourish in
some areas allowing residents and businesses to save on energy costs and reduce their
environmental footprint, while other areas effectively bar small wind.
Environmental review: like all construction projects, wind turbines have impacts on their
environment. Qualified biologists must review each project, and the impact of the wind
turbines is specific to the ecosystem they reside in. These reviews generally take at least one
year, and are often delayed by qualified unknowns, and sometimes excessive caution. In many
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•
•
cases, there are no data to assess how a wind turbine will affect a particular species, in
comparison to transmission lines, for example, which have over 50 years of history to document
their impacts. In general, wind turbines create less of an environmental impact than other
structures, but their risk to birds and bats has gained significant attention. The risk to most
avian species is well documented and many successful mitigation strategies are available.
Community acceptance: ultimately approval for a wind power project comes from locally
elected officials who should reflect the concerns and interests of the community. Generally, an
informed public is accepting and positive towards a well planned, well sited wind power project.
This has been the case in the United States and Europe. The project can bring economic and
environmental benefits, such as local jobs. However, poorly planned projects without
community participation have been problematic, although that is the case for all large
construction projects.
For small wind, identifying the resource: the cost, effort, and time involved in assessing
whether a home owner or farmer has enough wind on their property to put up a wind turbine is
often a barrier to small wind. Free wind maps often suggest a wind resource and are the first
place someone should look to check their wind; however, these maps cannot accurately identify
the wind at a particular site where nearby features such as a small hill or barn may dramatically
change the wind. The most accurate method is to measure the wind directly at the site for
approximately one year. Unfortunately, the cost just to assess the wind resource may nearly
equal the cost to install the wind turbine itself, and this has discouraged many small wind
projects.
Wind Power Potential for Monterey County
Figure 1 shows the wind resource at 70 meters and indicates a small dark green area of a “fair” wind
resource in the Salinas Valley of Monterey County, California. Community-scale wind power projects
generally build turbines between 50 and 70 meters in height so these maps indicate a “marginal” or
“fair” wind resource may exist for community scale projects.
Although some of the peaks and ridges within Monterey County have a potential wind power resource,
these areas are small, without good road access, and away from electric power system connections.
Additionally, wind turbines along ridges tend to have a larger visual impact since they are sky-lined. The
center of the Salinas Valley, however, offers the best potential for wind power development where
electrical substations for connection run along highway 101 and the road infrastructure allows easy
transport of the turbines to the site.
The modeled and measured data used to create the maps above along with additional measured data
analyzed by the authors confirm that the area south of Gonzales and north of King City have through the
year a “marginal” or, at best, “fair” wind resource. This observation likely eliminates Monterey County
from commercial wind power development as these projects require much faster wind speeds.
The wind resource in the Salinas Valley, however, has one unique characteristic that may open the door
for community scale and small wind development for local residents. It blows almost entirely during the
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summer afternoons when a large thermal gradient between the cool Pacific Ocean and the hot San
Joaquin Valley drives a sea breeze that rushes south down the valley and accelerates through the
narrowest part near Soledad. The chart below indicates why wind power during this time is more
valuable than wind power the rest of the year, and why Salinas Valley residents may find a way to save
on their electricity bills.
An Opportunity for Monterey County in Wind Power Pricing
Commercial utility-scale
wind power project
Sells electricity to PG&E at a power
purchase agreement rate
1 kWh of wind power earns 11 cents1
Community-scale/small
wind power project
Enters net metering program with PG&E;
credited for excess electricity produced
1 kWh avoids the purchase of
electricity at 17-20 cents/kWh2
1. Based on renewables receiving the 20 year 2009 Baseload market price referent (California PUC)
2. Based on agricultural power electric schedule for summer load (PG&E)
Now using the chart above, if the lower wind resource in the Salinas Valley means a wind turbine
produces electricity for 15 cents a kWh, the wind turbine would be a financial failure as a commercial
project, but a cheaper alternative to purchasing electricity from PG&E for a community-scale or small
wind project. Over the general 20 year life of a wind turbine this could add up to significant energy
savings, especially for large customers.
One data set from an anemometer showed that between 12 and 6 pm during the month of July in 2008,
a wind turbine was operating at full power just over 90% of the time. This is when customers are paying
the most for electricity when they could be generating their own on site at a potentially cheaper price.
Additional measured wind speed data in the Salinas Valley is needed to confirm the wind resource and
further financial analysis will prove or disprove the potential for local residents to harness wind power
for economic and environmental benefit, but the initial data assessment shows strong potential.
Soledad Project Overview: A Potential Wind Power Plan
The City of Soledad, located in the Salinas Valley, was the fastest growing city in California in 2008. It
has begun large infrastructure projects to support and serve its growing population. These include
upgrades at the electric substation on the north end of town near the freeway and expansion of the
wastewater treatment facility. As part of the expansion plan of the wastewater treatment plant west of
the town near the Salinas River, the city is considering powering the plant with wind turbines.
The installation of wind turbines is projected to save on the energy costs providing electric power to the
plant and reduce the city’s greenhouse gas emissions. Over the life of the project, the wind turbines are
likely to provide electric power from the “free” wind at a lower price than the electric power can be
purchased from the utility. When the wind blows, the electricity generated by the turbines will displace
the purchase of more expensive electricity, especially during the summer afternoons when electricity
prices are highest.
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Currently the city is measuring the wind resource on site to confirm the wind resource that the satellite
and modeled wind data suggests. Once this data has been collected as part of a collaborative effort
with the Stanford Solar and Wind Energy Project (http://swep.stanford.edu/), it will be analyzed to
assess the economic performance of the proposed wind power project. If this project moves forward it
will be an excellent example for other Salinas Valley cities and residents of how to take advantage of the
county’s renewable energy resources and serve as a test case for wind power in Monterey County.
III. Risk Study of Wind Turbines to the California Condors
Several wind energy projects have been considered in Monterey County in recent years. However, there
is a great deal of concern regarding the compatibility of such wind development and the California
Condor in this area. The authors proactively and voluntarily analyzed wind data and California Condor
movement data to determine if any areas in Monterey County have sufficient wind and where condors
generally do not utilize the airspace.
Methodology
Geographical Information System (GIS) was the technical framework of data processing and analysis in
this project. ESRI ArcGIS 9.3 was the main GIS software platform. Methods of release to the wild and
GPS attachment were described in Sorenson and Burnett (2007). These GPS data represent a total of 27
different individuals between July 2003 and September 2008. A sample of the GPS data is shown below.
Each row contained a condor flight record. The table was “Geocoded” into a map layer, where the
longitude and latitude data referenced as coordinates and every record was transformed into one point
feature on the map. Then the map was overlaid on a digital elevation model data layer (DEM). DEM is a
representation of continuous elevation values over a topographic surface (Figure 2). At every condor
flight location, an above ground-level height (AGL) was calculated as condor flight height subtracted by
its orthogonal ground elevation. As the commercial scale wind turbine, like the Vestas V90 3.0 MW
machine, will reach approximately 135 meters above the ground at the tip of the top blade, we focused
on the locations with AGL under 200 meters since these areas would have the greatest risk to free-flying
condors relative to wind energy construction.
Two issues about GPS data accuracy need to be clarified here. First, the 50 gram Argos/Solar PTT was
the GPS transmitter deployed in the project and was made by Microwave Telemetry and has a reported
altitude error of 22 meters. This means that the accurate elevation might be 22 meters more or less
than the data in the record. Microwave Telemetry conducted a stationary test of the altitude data with
16 GPS units they assembled prior to deployments, including several units later deployed on California
Condors represented in this study, and found that out of a total of 908 observations, 98.6% of the
altitude measurements were within 22 meters of the test site (Cathy Bykowsky, Microwave Telemetry,
Pers. Comm. October 15, 2009). Topography, canopy cover, and animal behavior affect fix rates and
location error of GPS collars with best results in less mountainous terrain and more open canopy (D’Eon
et al 2002 and Cain et al 2005).
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Second, the transmitter could only record 2047 meters as maximum. All the values over 2047 revolved
back to zero and began counting again at 0. For example, if the condor flight was at a height of 2547
meters, the value would be recorded as 500 meters (2547-2047=500). As a result, some records
reported as under 200 meters AGL (87,071 in total) might be included inappropriately since they could
actually be of condor flights at the much higher AGL. However, the result represented a more
conservative analysis and should be still considered as a valid reference in the decision making since this
limitation of the GPS AGL data can only lead to a false positive in the analysis. The use of 200 meters
also represents a buffer of 65 meters above the top of the tallest wind turbine likely to be installed in
Monterey County which is justified given the potential error in altitude data caused by topography,
animal behavior and perhaps other factors.
Microsoft Access Database of GPS Condor Movement Data
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Figure 2 – Condor Detections in Monterey County between July 2003 and September 2008
with Digital Elevation Model Topography Overlaid
Figure 3 – Condor Detections in Monterey County between July 2003 and September 2008
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Figure 4 – Condor Detections in Monterey County between July 2003 and September 2008
below 200 Meters Above Ground.
Figure 3 shows all condor detections (n=132,701) between July 2003 and September 2008 and Figure 4
shows all detections where condors flew or landed below 200 meters above ground level (n=87,071).
This ground to 200 meters high zone represents the airspace that may be occupied by the tower or
blades of the largest commercial wind turbines. Although we do not know the behavior of condors in
the presence of turbines, the records indicate areas where a condor has historically flown or landed, and
any wind turbine erected there is likely to increase the probability for an encounter of a condor with a
wind turbine. These encounters may pose risks from blade strike to these endangered birds, as they
have to a variety of other birds.
Figure 5 shows condor detections within 0-200 meters with the addition of the wind resource by wind
power class overlaid. The GPS condor movement data shows a trend that condors in Monterey County
do fly high over the Salinas Valley likely similar to how the birds travel over the Cuyama Valley as
discussed earlier. South of King City along the Salinas Valley, the valley floor is narrow and foothills on
both sides of the Salinas River nearly come together. Condors were documented flying within 200
meters above ground level in this area, which is consistent with the typical movement patterns of the
birds. In addition, the area immediately north and east of King City is designated an Important Bird Area
by Audubon California (see http://ca.audubon.org/maps/pdf/King_City_Grasslands.pdf for detailed
map and description). Therefore, this area is a poor choice for wind energy development with regard to
condor conservation.
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Figure 5 – All Condor Detections in Monterey County between July 2003 and September 2008
below 200 Meters Above Ground with the Wind Resource Overlaid.
Recommendations and Limitations of this Study
This study begins to illuminate the risk of wind turbines to the California Condors and potential siting
strategies such that wind power development can begin in Monterey County. As with all studies, there
are limitations stemming primarily from the limited data set and the fact that condor habitat and
behavior may change over time. These limitations include:
First, only approximately 25% of the free-flying population was tagged with GPS. Therefore, the exact
movements of the untagged 75% of the population are unknown. Areas not documented as condor use
areas in the report could be used by an individual not tagged. However, there is no reason to believe
that these data do not represent the normal movement patterns of condors in the region. Nevertheless,
it is conceivable for a condor to wander into valley bottoms such as the Salinas Valley.
Second, California Condors are largely dependent on food provided by release programs, also referred
to as proffered food. Therefore, their movements might be to some extent influenced by external
factors. Over time we can expect the birds to utilize their former range more evenly spread throughout
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areas where they would normally go. Condors are largely dependent on food because proffered food is
a main strategy to reduce the impacts of lead poisoning. The carrying capacity for condors in the region,
the number of animals an area can support, is unknown. In Big Sur, California despite the intensive
feeding program, a total of 26 non-proffered carcasses were fed upon by Big Sur Condors between
March 1999 and June 2006 (Sorenson and Burnett 2007) and in just the last three years another 50
carcasses were fed upon (Burnett pers. comm.), which suggests the birds are becoming more effective
at finding their own food despite the food provisioning by biologists. California Sea Lion (Zalophus
californianus) was the most common food item found by free-flying condors in Big Sur. Nevertheless, it
can be expected that condors will at least move greater distances and perhaps will frequent areas now
under-utilized, particularly in the areas where topography and other habitat requirements exist for the
birds. Therefore, monitoring should continue and use maps periodically updated. Proposed projects
should use the most current maps.
In six years of GPS monitoring of certain condors representing all age classes, only one detection point
occurred below 200 meters along a narrow strip north of King City to south of Gonzales. Soledad is
situated in between the only two active condor release sites in Monterey/San Benito Counties. Condors
are opportunistic and commonly take advantage of the proffered feeding sites at both release areas. As
a result, condors routinely fly over the Salinas Valley. We believe that normal movement patterns even
after food subsidy for the birds is curtailed or discontinued would remain the same in this part of
Monterey County primarily due to its topographic features. Large numbers of ungulates likely inhabited
the Salinas Valley at one time, but those conditions no longer exist and therefore foraging opportunities
for the birds in this area are rare. In addition, there are no nesting or roosting areas in this part of the
valley either. In the absence of these habitat requirements, there are no attractants for the birds. To
our knowledge, there is no reason to believe that these conditions will change in the future.
The ability of condors to avoid wind turbines is unknown. Results from a study in Spain (Lucas et al
2004) suggest that some large soaring birds, such as Griffon Vultures (Gyps fulvus) do avoid wind
turbines in most, but not all, situations. Despite high numbers of Griffon Vultures traveling through the
Strait of Gibraltar, only one Griffon Vulture was found dead while conducting twice weekly carcass
searches for a period of 14 months. Nevertheless, for slow reproducing species such as California
Condor, this rate would be too high. A key difference between the Straits of Gibraltar wind farm and the
Salinas Valley is the former is along ridges and the latter is along a valley floor. Although the Griffon
Vulture is very similar to the California Condor in nearly all respects, and particularly in flight, we have
no way of knowing how condors would react to wind turbines. Annual mortality rates for Turkey
Vultures (Cathartas aura) in the Altamont Pass Wind Resource Area, California were considerably lower
than for raptors as a whole (Small and Thelander 2008), but fatalities did occur for this species and at
rates too high if it were California Condors.
In Monterey County, where sufficient wind exists for energy development, all but one area should be
abandoned in terms of wind energy development based on these results. Along a narrow strip on the
Salinas Valley floor between north of King City and south of Gonzales appears to be one location where
the risk to condors is probably lowest and a sufficient wind resource exists.
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Based on the results and limitations of this study, we make the following recommendations (only insofar
as the California Condor):
•
•
•
•
•
Prohibit the construction of community and commercial scale wind energy in all areas where
condors frequent in Monterey County within 200 meters above ground level.
Consider development of wind energy, at any scale, along a narrow strip on the Salinas Valley
floor between north of King City and south of Gonzales.
Where wind energy is permitted, cattle grazing or any other activity that would lead to large
mammal carcasses (i.e. grazing) or large numbers of small mammals (i.e. ground squirrel
shooting) should be avoided so as to not attract scavengers to the site.
Require pre and post construction monitoring of birds and bats as per state guidelines
(California Energy Commission and California Department of Fish and Game 2007).
Continue California Condor GPS monitoring in Salinas Valley and update use maps periodically.
We hope this study’s results and recommendations can assist policy makers, wind power developers,
and the environmental community in Monterey County in making an informed decision as to the siting
policy of potential wind power projects such that the risk to the California Condor is minimized to the
fullest extent while allowing certain Monterey County residents to tap their wind resource potential for
economic and environmental benefits.
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