Wind energy/avian impacts in western NC 1
Potential Avian Impacts of Wind Energy Development in Western North Carolina: A Literature Review
prepared by
Curtis Smalling
Ecos of the Blue Ridge
667 George Moretz Lane
Boone, NC 28607
For
The Department of Technology
Appalachian State University
Boone, NC
January 2003
Scope of This Review
This review attempts to synthesize a number of recent and past studies in the peer reviewed, governmental, and industrial literature concerning the actual and potential impacts of wind development on avian populations. The literature was also reviewed specifically to address issues and avian studies relating to North Carolina. An overview is also attempted of the major avian conservation initiatives in the Southern Blue Ridge. These conservation initiatives present both obstacles and opportunities for wind development in the mountains of western North Carolina.
The avian life of the Southern Blue Ridge is one of the most diverse in the east with over 160 breeding species (Hunter et al, 1999). This review will address the composition of the avian community throughout the year, with an emphasis on species of conservation concern and their potential use of wind resource areas.
The Department of Technology and Dr. Dennis Scanlin at Appalachian State University are to be commended for their efforts to assess avian impacts early in the planning and study period. While it is readily apparent that wind energy can and does have impacts on the avian and natural communities, those impacts may be mitigated or avoided with careful and thorough research of potential sites, as well as the experience of other wind development areas across the country.
Oversights, misinterpretations, and errors are the author’s alone. This review is a jumping off point for further research as we search for low impact, renewable sources of energy.
The Potential Avian Impacts of Wind Resource Development in Western North Carolina:
A Literature Review
Scope of this Review…………………………………………………………………. …...2
Contents….………………………………………………………………………..………3
Introduction………………………………………………………………………….…….4
Avian Mortality Issues…………………….……………………………………..………..5
Overview of Current Research……………………………………………………8
National Research Findings...……………………………………………..……..10
Avifauna of Western North Carolina………………………………………………….…16
Brief History of Ornithological Study in the Region…………………………….17
Species of Special Concern………………………………………………………19
Temporal and Spatial Considerations……………………………………………………27
Winter Bird Use………………………………………………………………….27
Breeding Season………………………………………………………………….28
Migration Seasons………………………………………………………………..29
Nocturnal Species………………………………………………………………..36
Raptors…………………………………………………………………………...36
Habitat/Species Relationships……………………………………………………41
Avian Conservation Overview…………………………………………………………...46
Partners in Flight Plan……………………………………………………………47
National Audubon Society Important Bird Areas Program……………………...48
Southern Appalachian Forest Coalition………………………………………….49
Recommendations………………………………………………………………………..51
Literature Cited…………………………………………………………………………..54
Appendix I (Species of the NC Blue Ridge)…………………………………………..…69
Appendix II (NC Bibliography)…………………………………………………………74
Appendix III (Helpful Internet Resources)………………………………………………81
Introduction
Wind energy development appears to be gaining momentum as an commercially viable source of energy across the country. The harnessing of wind power provides an alternative to the traditional methods of power generation that appeals to an ever more environmentally aware populace.
But wind energy does not enjoy universal acceptance. Communities faced with wind energy development often reiterate concerns over viewshed protection, property values, noise, and environmental impacts. Opponents often cite the avian impacts of wind development as a major obstacle to and drawback of wind energy.
As wind energy resources are studied for development, several issues related to avian issues arise. As is stated in the Proceedings of the National Avian/Wind Power Planning Meeting, there are certain things we know about the relationship of wind energy development and birds. These include the fact that birds are killed at wind turbines, the impacts of those deaths can be significant (or insignificant) to local bird populations, bird usage and risk vary among different sites across the country and the world, bird usage and risk may vary within a single site, raptors are at high risk at some sites and little risk at some sites, and nocturnal migrants may be at higher risk at some sites. Additionally, the only way to mitigate the risk to birds is to situate the wind energy development in areas of low bird use (PNAWPPM-IV, 2001).
It follows from these items that is is important to answer some basic questions about potential sites prior to development in an effort to reduce bird impacts. Some of these questions are:
How many birds use the proposed site?
What kinds of birds use the proposed sites?
How is that usage related to the time of year? Time of day?
What are the species of special concern that may be impacted?
Does development have the potential to impact the populations of those species of high priority?
Can research conducted at proposed sites identify potential impacts and possibly address mitigation strategies prior to construction?
This review will look in detail at these facts and questions and summarize how what we know about the national impacts of wind development can be related specifically to North Carolina.
Avian Mortality Issues
The development of wind energy resource and generation areas creates risk for avian species. These risk factors take many forms including :
- Hard structure kills (turbine blades, towers, weather towers, guy lines)
- Population effects (reduction in use, increase in use, nest productivity)
- Electrocutions from transmission lines
Many other forms of human caused mortality affect bird populations in the United States. Most of these other causes (vehicular collisions, window strikes, communication tower kills, and powerlines) annually kill millions of birds. Wind turbine mortality is much lower and is on the magnitude of just over 2 birds per turbine/ year nationwide or about 33,000 birds killed per year. The recently published Avian Collisions with Wind Turbines: A Summary of Existing Studies and Comparisons of Avian Collision Mortality in the United States (Erickson et al, 2001) summarizes the known data from collision sources of mortality:
*Vehicles60-80 million
*Buildings and Windows98-980 million
*PowerlinesTens of Thousands-174 million
*Communications Towers4-50 million
*Wind turbines10,000-40,000
(from the Executive Summary, Erickson et al, 2001)
Erickson’s estimates are based on published studies from a wide range of sources and account for the wide ranges of estimated mortality. This study is available online in full text format at and includes an extensive bibliography for each of the listed causes of avian mortality.
One thousand thirty-three carcasses were found at wind resource developments during the reporting period covered in the Erickson study (1999-2001). Eight hundred forty-one of these carcasses were at California sites. Of these, 40% were diurnal raptors, 19% were protected passerines, 11.5% were owl species, and 11% were unprotected species (House Sparrow, European Starling, Rock Dove). The remainder were various waterbirds, waterfowl, shorebirds and others. Estimates of nocturnal migration kills range from 2.6% to 10.2% of all carcasses. This number may be low as carcass removal by scavengers is much faster for smaller passerine species, which are more likely to be nocturnal migrants.
For non-California sites, 192 carcasses were reported. Of these, only 3% were diurnal raptors, 78% were protected passerines, 3% were non-protected birds, 0.5% were owls, and 5% were waterfowl. Estimates of nocturnal migrant mortality ranged from 34% to 60%. This percentage of nocturnal migrants is much higher than the California estimate. This discrepancy may be due to search methodology. California wind farms tend to be much larger than other sites and searches are conducted less frequently and often do not include the entire wind resource area. It may simply be that non-California sites have higher usage and passage rates for nocturnal migrant birds.
Erickson et al. estimate national bird mortality to be 2.19 bird deaths per turbine per year for all species (total carcasses at studied sites/total number of turbines at studied sites). Raptor specific mortality is estimated to be .033 birds/turbine/year. Ignoring California data yields estimates of 1.825 birds/turbine/year and 0.006 raptors/turbine/year. These estimates suggest that avian impacts from wind development will probably not have population level effects for most species. However, species of small population size, limited geographic distribution, or high sensitivity to development might be adversely impacted.
Overview of Current Research
Even though wind energy development has been seriously considered as a viable energy alternative on a commercial scale for decades, the potential for avian impacts of that resource development did not receive rigorous attention in the United States until the early 1990’s. Part of the impetus for this attention was a ruling in United States court on the negative consequences of bird impacts, especially liability issues related to the deaths of individual birds protected under the Endangered Species or Migratory Bird Acts (Sinclair, 2001). This ruling, and public and professional concern over the unknown impacts of wind energy development on bird communities, prompted the Department of Energy in 1992 to direct the National Renewable Energy Laboratory to establish a direction for future research on the issue. The Avian Subcommittee of the National Wind Coordinating Committee was formed after the first National Avian -Wind Power Planning Meeting held in Denver in 1994 (PNAWPPM, 1995).
That meeting was the first chance for a variety of stakeholders to meet to discuss current research and to make recommendations for the future. Most of the projects in the first few years of research were in the American West and included the Altamont Wind Resource Area (CA), Norris Hill Wind Resource Area (MT) (Harmata et al., 1998), and Tehachapi and San Gorgonio (CA). For a review of the research programs funded and underway in 1997, see Sinclair et al. (1997).
It became apparent that a standardization of methodologies for studying mortality would be beneficial for future planning. These standards would allow for comparison among different studies and wind resource areas. The second Planning Meeting was held in Palm Springs, CA, to solidify plans for standardizing methodologies and for further updates on current research (PNAWPPM-II, 1996). Three documents were produced shortly thereafter. These include “Studying Wind Energy/Bird Interactions: A Guidance Document (Anderson et al., 1999), “Avian Risk and Fatality Protocol” (Morrison, 1998), and “Development of a practical modeling framework for estimating the impact of wind technology on bird populations.” (Morrison and Pollock, 1999). Specific study methodologies will be discussed elsewhere in this review.
These publications and studies were followed closely by Planning Meetings III (1998) and IV (2000). At these meetings presenters reported on ongoing research projects as well as new findings on technological concerns (i.e., motion smear, acoustics). These proceedings have been published as well (PNAWPPM-III, 2000 and PNAWPPM-IV, 2001). A further update on current research was also published in 1999 (Sinclair, 1999). Additionally a comprehensive review of avian mortality from collisions with man made structures has been completed. (Erickson et al., 2001; see avian mortality issues section above).
The four planning meeting proceedings form the core of the Wind Power/Avian Impacts literature to date. Most Department of Energy funded studies are summarized in these four documents, as well as summaries of international findings (See Winkleman 1995, Dirksen et al., 2000, Janss 2000, and Lowther 2000). The literature pertaining to avian impacts of wind development is updated frequently at the website of the National Renewable Energy Laboratory at This database currently (accessed 11/1/02) contains some 1800 citations. Full text of most DOE funded research as well as other NREL findings, protocols, and studies are available on line from
National Research Findings
Since the formation of the Avian Subcommittee of the National Wind Coordinating Committee, many research projects have been funded and conducted with the standardized goals and methods of the working group as a guide (Anderson et al, 1999). The seminal “Studying Wind Energy Bird Interactions: A Guidance Document” has moved the study of wind power impacts on avian populations far ahead of where the industry was just a decade ago. Regular stakeholder conferences and reports (PNAWPPM, 1995; PNAWPPM-II, 1996; PNAWPPM-III; PNAWPPM-IV, 2001) have allowed studies in differing regions of the country to share findings, evaluate each others data, and produce findings of use to other planners and scientists.
One of the primary goals of the national wind research program is the standardization of methodologies (PNAWPPM, 1994). The work of Anderson et al, (1999) has laid out the basis for standardized efforts nationwide to allow planners, researchers, and reviewers to compare results in differing areas. The ultimate goal is to produce Before-After/Control- Impact (BACI) studies for wind sites. These studies require site studies before development, including control plots areas unaffected by eventual construction. These baseline usage patterns, natural mortality rates, species richness and abundance, and other measures are then repeated on the treatment area and control after development.
These base level studies are collectively labeled Level 1 studies by the NREL Avian Subcommittee protocols (Anderson et al, 1999). Level 2 studies address specific higher order issues such as long term population impacts, cumulative effects (noise, maintenance, traffic, etc), population modeling projects, and manipulative studies to clarify risk issues. Also included in this standardized approach are risk reduction studies. Current work on avian hearing and the use of noise as a deterrent (Dooling, 2002), motion smear (that is, the effect of the turbine blades becoming less visible as they spin) (McIsaacs, 2001; Hodos et al., 2001), lighting, prey abundance, and other testing of methods of reducing avian use of wind development areas or risk of collision and mortality with turbines.
To date, several major wind development sites have published major studies (Sinclair, 2001). Some of these studies and their findings will be reviewed below.
Altamont Wind Resource Area, CA
The Altamont site is a very large site including some 5400 turbines arranged over 150 km2. Discovery of Golden Eagle and other raptor carcasses spawned research on bird use of the area including current studies on population and foraging ecology of raptors at the site. This study has shown that despite initial suggestions that perching behavior and electrocution might be major factors, it now appears that turbine spacing and the increase in prey abundance on the site may increase risk to Golden Eagles, Red-tailed Hawks, and American Kestrels. Some of the research findings have found an increase in prey abundance and raptor use associated with foraging in the turbine area. There is still debate over whether mortality is significantly higher at the gaps between strings of turbines versus within string locations. Mortality at the varying tower, turbine, and topographies in this extensive site are still being studied. Raptor mortality remains higher at Altamont than at any other site in the country. The top five most commonly killed species are Red-tailed Hawk, Golden Eagle, American Kestrel, Turkey Vulture, and Common Raven. Raptors make up 54% of all bird carcasses found (Thelander and Rugge, 2000; Hunt et al, 1995; Hunt et al, 1997; Hunt et al, 1998; Hoover et al, 2001; Smallwood et al, 2001).
Tehachapi and San Gorgonio Wind Resource Areas, CA
These paired studies have examined baseline usage of the two sites and found lower levels of mortality than at Altamont. This study has pointed out that usage rates, mortality rates, and risk rates vary, both within and among sites. San Gorgonio contains a wetland within its resource area and so bird utilization rates are higher than at Tehachapi. Tehachapi has a higher mortality rate than San Gorgonio however, probably due to the types of birds present and their foraging patterns. Both sites found significantly lower rates of usage and mortality for raptor species than Altamont. Also at both of these sites, mid turbine string mortality was higher than gap mortality, unlike Altamont (Anderson et al, 2001).
Foote Creek Rim Wind Resource Area, WY
This study includes a test of Ultra Violet coatings treatment of turbine blades. Results show that UV treatment may not work and may attract birds instead. Estimated mortality here was just under 2 birds/turbine/year consisting mostly of nocturnal passerine species. Also this study suggests that 85% of diurnal raptor activity occurs within 50 meters of the canyon rim or escarpment and recommends placing turbines greater than 50 meters away from edges (Strickland et al, 2001a).
Norris Hill, MT
This extensive radar and visual study of a proposed wind energy development site examined bird usage rates at the proposed wind resources area. High estimated numbers of migrants (over 7 million birds within the study area in fall and 3.4 million in spring) make this one of the heaviest avian use areas documented in wind related studies. Most birds passed at a mean height of about 250 meters in fall and about 400 meters above ground level in spring. This is the first phase of a Before/After – Control/Impact (BACI) study. This wind development has however been put on hold indefinitely so the after development study will probably not be completed. This study also contains a great deal of information regarding methodology for future radar studies including suggestions for sampling effort and efficacy of the method (Harmata et al, 1998 and 1999).