Reducing Wind Energy-Related Mortality in Threatened Raptors

Wind turbines pose a greater threat to threatened species, like the California condor.

Wind turbines pose a greater risk to threatened species, like the California condor.

Sheridan Devlin- Environmental Science

Rebecca Haber- Pre-Veterinary Science


Rehabilitators took California condors into custody in order to secure their population in the 1980s (Avants, 2016). Recently they released Condor AC-4, a male in the California Condor Recovery Program, back into the wilderness. AC-4 fathered the first captive-born chick and through controlled breeding in captivity, the number of California condors rose from 22 to 435 (Avants, 2016). After spending 30 years in the San Diego Zoo Safari Park, rehabilitators finally gave him a clean bill of health and decided he was fit to return to the wilderness again after blood levels indicated low lead content (USFWS, 2016). AC-4 serves as a reminder that the California condor’s population is still slowly recovering. This threatened species still requires protection, and wind energy–lauded for its environmental benefits–could ironically and unintentionally lead to their extinction (Platt, 2013).

Despite the threat to condors, it is also vital that the U.S. generate and efficiently utilize clean energy in the face of global climate change (Abraham, 2015). Wind energy offers a cleaner alternative to fossil fuels such as coal and natural gas, making it the second fastest growing renewable energy source worldwide (USDE, n.d; Wind Energy Foundation, 2016). Burning fossil fuels has significant environmental repercussions that cause air pollution from the release of nitrogen and sulfur oxides (EPA, 2016). As discussed by the Wind Energy Foundation (2016), “[Wind energy] has virtually no polluting properties or side effects” (“What Is Wind Energy”) making it a more environmentally sustainable option. Wind power functions on the basis that wind can be harnessed to generate electricity through use of wind turbines (Wind Energy Foundation, 2016). A wind turbine is a structure with two or three blades attached to a rotor. The blades spin as wind passes through them, which moves the rotor and generates electricity (Wind Energy Foundation, 2016). While wind offers a cleaner alternative to the combustion of fossil fuels, it does not come without setbacks; wind energy has long been criticized for its impact on birds, specifically raptors (Beston, Diffendorfer, Loss, & Johnson, 2016). Trends show wind energy will continue to develop rapidly in the near future with growth as high as 600% in the U.S. alone (Subramanian, 2012; Wind Energy Foundation, 2016; USDE, n.d.). As the industry continues to advance, the risks that wind turbines pose to raptors will increase accordingly, and therefore steps to reduce this threat must occur sooner rather than later (Erickson et al. 2002).

There is consensus among researchers that wind energy has some impact on most bird populations (Shaffer & Buhl, 2016). However, many agree that as a whole, the impact on bird populations from wind energy does not pose a significant threat (Bassi, Bowen & Fankhauser, 2012). Beston et al. (2016) state that the percentage of all U.S. mortalities that are due to wind turbines was less than 0.05% for most species (Fig.2A). With the goal of educating the public on the concerns surrounding wind power, the Centre for Sustainable Energy (2011) stated that although the industry takes responsibility for causing some fatalities,

“Wind turbines represent an insignificant fraction of the total number of bird deaths caused by man-made objects or activities” (p.32).

However, species with small breeding populations or low rates of reproduction experience more severe effects on their relative population size from mortality due to wind turbines, in comparison to those with normal or large breeding populations globally (Beston et al., 2016). Beston et al. (2016) state that the Blackpoll warbler, a species with a low rate of reproduction, had the highest risk assessment values (indicating a high risk for population decline) than any other species analyzed (p.8).  Since raptors are long-lived birds and are higher up on the food chain, the risks are increased (Ehrlich, Dobkin & Wheye, 1988).

If species with small breeding populations or slow reproductive rates possess behavioral patterns that predispose them to collisions with turbines, the ill effects from wind energy can be significant (Rivers et al., 2014; Subramanian, 2012). Several behavioral characteristics make raptors more vulnerable to collision with turbines (Miller et al., 2014; Rivers et al., 2014). According to Powlesland (2009), raptors are “large soaring species with poor flight manoeuvrability” (p.17) which makes them more susceptible to collision with turbines. Puckett (2009) cites Hoffman, executive director of Audubon (a bird conservation organization), who states that raptors are constantly looking at the ground for food, rather than looking ahead for potential objects that could harm them. Raptors prefer high altitude wind and the turbines use that same wind to function properly (Subramanian, 2012). This high altitude wind allows them to soar long distances while expending minimal energy, however, this behavior puts them at greater risk for direct collision with moving turbine blades (PBS, 2008).

California condors reproduce at a slow rate and possess specific natural behaviors that put them at a higher risk for collision with turbines over other avian species (Powlesland, 2009). During the 1980s, California condors were classified as highly threatened, as population levels were drastically low (Snyder & Johnson, 1985). By 1982, there were only 23 remaining California condors nationwide (Snyder & Johnson, 1985) and today, according to National Geographic (2016), there are approximately 127 in the wild. Due to the California condor’s critically endangered status, any mortality events (such as those from wind turbines) are considered a substantial loss to their population (Rivers et al., 2014).

Unfortunately, condors possess certain behaviors that often result in their death (e.g., perching on power lines) (Bryce, 2016). In 1993, a young condor was electrocuted while attempting to join several other condors atop a power pole in California (Meyers, 1993). Witnesses report that the bird landed on two separate lines, which completed a deadly circuit and struck the condor with 17,000 volts of electricity (Meyers, 1993). The condors’ large size contributes to their heightened risk; unlike small birds that can land on a single power line, condors are more likely to land on multiple power lines which can lead to electrocution and death (NPR, 2015). In effort to combat condor behaviors that increase their risk for deadly collisions, behaviorists at the San Diego Zoo Safari Park implemented “condor power line aversion training programs” (NPR, 2015) for condors in captivity, in order to train the birds to avoid perching behavior in the wild. Michael Mace, curator of birds in the San Diego Zoo Safari Park, states that their objective is that the aversion therapy will allow the next generation of condors to mimic the behaviors of their parents, and they hope that ultimately the dangerous behavior can be unlearned (NPR, 2015). If power lines are a risk, the same can be said about wind turbines, as both provide a medium for condors to perch on. These programs can benefit California condors further by reducing perching behavior on wind turbines.

When birds of prey decrease in population size, the food chain adjusts, which subsequently leads to an overabundance of invasive species that cause damage to the surrounding ecosystem (Ehrlich, Dobkin, & Wheye, 1988). As the California condor is a crucial part of a balanced ecosystem, it is paramount that wind farm operators take the necessary precautions to avoid extinction. In order to minimize the effect of wind turbines on threatened raptors, legislation should be passed that requires wind energy companies to implement radar systems that halt turbine blades as endangered birds approach. California condors are covered by The Endangered Species Act of 1973, which helps reduce threats to species experiencing significant population decline, and that are facing either endangerment or extinction (EPA, 2016). Wind energy companies face serious legal ramifications for causing the deaths of protected birds, and thus the wind energy industry needs to take precautions to reduce the potential of condor mortality. The current climate for endangered species prompted the U.S. Department of Justice to uphold strict regulations in order to protect threatened birds from unlawful killing by wind energy companies (DOJ, 2013). In response to a lawsuit in 2004 against a large wind farm called the Altamont Pass in California, criticized for its’ high rate of raptor mortality, wind farm companies and county officials agreed to temporarily shut down half of the wind turbines in the winter, during the breeding season of most condors (Powlesland, 2009).

In an effort to protect California condors, there must be legislation in place that regulates wind turbines, similar to Assembly Bill 821 that was introduced to protect birds from lead poisoning in 2007 (Jurek, 2014). This bill created a lead-free zone within the range of the California condors’ breeding grounds, in an attempt to minimize mortality from lead poisoning (Jurek, 2014). The decline in the population of California condors can be traced back to lead poisoning, through spent lead ammunition (Rivers et al., 2014). According to U.S. Fish and Wildlife Services (2016), California condors possess foraging practices that make them more vulnerable to lead toxicosis from consuming carrion contaminated with lead. The USFWS (2016) found that lead poisoning in condors can cause difficulty feeding, mating, nesting, and death. Since the passing of Bill 821, there has been a 98.89% hunter compliance (Hunt For Truth Association, 2014), indicating the effectiveness of legislation as a form of regulation, and the willingness of the public to comply with these standards.

There are several options for wind developers regarding future construction of wind farms such as strategic placement of turbines, altering the design of the blades, and increasing size of turbines (The National Wind Coordinating Collaborative, 2010). While these may be promising methods to employ in future construction of new wind farms, they do not address the problem presented by current wind farms that could cause significant mortality to threatened raptors. As an alternative, several companies created mitigation-based radar systems that minimize bird-turbine mortalities (e.g. DeTect, Inc. and the Gulf Wind Project) (Cook et al., 2011, p.38). According to Bryce (2016), many wind energy companies are opting for more bird-friendly adjustments to their wind farms. The Babcock and Brown company was the first to install such a system in Texas at the Gulf Wind Project in 2006 (Bryce, 2016). DeTect, Inc. later improved on the idea of a mitigation-based radar system, by developing a precision system for birds, called the MERLIN SCADA system (DeTect, 2016). The system is based on automatic mitigation techniques that provide constant, unattended data on bird activity over a radius of three to eight miles around a wind farm site (DeTect, 2016). The system uses algorithms to identify certain species of birds and only operates during conditions of perceived high risk of mortality to threatened birds (DeTect, 2016).

The MERLIN system was implemented at two operating wind farms in the U.S. in 2009 (Kelly, West, & Davenport, 2009). The system can be programmed to recognize and address mortality risks to condors (Kelly, West, & Davenport, 2009), such as idling turbine blades during times when condor activity is at its highest (Puckett, 2013). With strategic placement of the radar systems in areas that are dense with California condor breeding populations, wind turbine-associated mortality may decrease. By programming these systems to function solely under conditions of high risk, and by only targeting California condors, the cost to wind farm operators may not be significant (Lucas, Ferrer, Bechard & Munoz, 2012). Through the implementation of such mitigation systems, wind farm operators may also use the data that radar systems provide (such as passage rate and flight patterns) to more accurately assess the impact of wind turbines on California condors (DeTect, inc., 2013). Due to the fact that wind energy is a quickly developing and advancing industry, there is a need for advancement in preventative measures commensurately in order to sustain a delicate ecosystem (Bryce, 2016).

California condors are among many migratory raptor species that only pass through turbine blades occasionally and not for long periods of time (Subramanian, 2012, p.311). According to Drouin (2014), the deficit of energy due to the halting of turbine blades when high risk bird species pass through is not a significant loss to large-scale wind farm companies if programmed to operate only when threat to birds is considered abnormally high, as in the MERLIN SCADA system. In 2008, researchers in Spain implemented specialized stopping programs on various wind farm operations that selectively halt turbine blades as vultures (raptors) come within a dangerously close proximity to the turbine (Lucas, Ferrer, Bechard & Munoz, 2012). The system reduced the mortality rate of targeted raptors by 50%, with a subsequent reduction in total energy produced of only 0.07% per year (Lucas, Ferrer, Bechard & Munoz, 2012, p.84).

Since the installation of Rim Rock wind farm in 2012, two raptor fatalities were reported (Puckett, 2013). This prompted the wind farm to install a mitigation-based radar system. While the system has worked effectively, (Puckett, 2013) this is a retroactive, rather than proactive approach. In order to protect the California condor, and the ecosystem, it is important that legislation mandate the implementation of such systems in all wind farms that threaten the preservation of California condors before their impact results in the death of the species and subsequent extinction. Wind farms in California are beginning to implement similar systems, indicating the feasibility of the design. Puckett (2013) speaks of an operations facility in California that can halt wind turbines 1,200 miles away in Montana when flight patterns of raptors indicate risk of collision with turbine (para. 1). In fewer than 30 seconds, a tracking radar can identify raptor species and adjust turbine blade speed accordingly (Puckett, 2013). In California, large wind farms implemented condor detection and avoidance systems that slow down turbine blades and then stop completely if a condor comes within a certain distance of the turbine (Puckett, 2013). These projects show that the wind industry has the technology to quickly shut down turbines when condors are at risk. Rehabilitators can track each condor that was released due a transmitter that they attached to each bird (Avants, 2016).  If a condor is killed by the turbines, wind farm operators are required to further adapt their operations to turn turbines off completely during the day, when condor activity is highest (Platt, 2013).

While wind turbines do not currently pose a significant threat to most bird species, the increasing use of wind energy as a form of renewable energy can lead to the endangerment and extinction of threatened species such as the California condor (Subramanian, 2012). Mortality can be minimized through the use of radar mitigation systems that halt or slow turbine blades as birds are approaching during conditions of high risk of collision with wind turbines. This method would overall not be a significant cost to wind farmers when compared to the costs of building and maintaining wind farms (Lucas, Ferrer, Bechard & Munoz, 2012). Additionally, employing a mitigation based radar system would allow for researchers to create more statistically useful preventative measures to minimize mortality and optimize efficacy. It is useful to decrease the number of deaths of California condors for reasons such as legality, and to maintain the integrity of species that are approaching extinction. Without the negative connotations associated with wind energy regarding environmental impact on birds, wind energy may become an even more popular and efficient means of generating electricity.



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