Duke University
Nicholas School of the Environment and Earth Sciences
Bio 217




General Avian Impacts

Bird Site Assessment

Avian Solutions

About Bats and Wind Turbines

Bat Site Assessments

Bat Data and Diagrams


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Avian Solutions

It was previously thought that old turbines with smaller rotors and higher operational speeds contributed to avian mortality. However, new studies have shown inconclusive evidence about the effects of size and speed of the turbines. Many studies now take into account bird kills per MW to account for varying sizes of turbines and therefore wind swept area (circular area that the turbine blades cover in one full rotation). The old lattice structure of many turbines was also thought to be a threat to birds due to their propensity to use the structures for perching. Current literature on the subject shows this idea to be uncertain as well. (NWCC, 2004)(Smallwood and Thelander, 2005). The critical solution to avoiding avian collisions is the SITE ASSESSMENT. This is the only tool to allow wind developers and other stakeholders to determine if they are building farms in sensitive avian habitat.

The California Energy Commission recently came out with a suggested list of Impact Avoidance and Mitigation terms for new wind farms. They state that on a macro scale wind farms should not be placed in areas highly used by declining or threatened avian species; Nothing takes the place of well run pre-permitting avian studies, as mitigation techniques employed after the wind farm is built can be costly and require periodic and/or seasonal shut downs of the turbines. On the micro-scale there are many avoidance strategies that can be employed to reduce impacts to the surrounding ecosystems:

  1. Minimize fragmentation and habitat disturbance by placing roads, turbines and other infrastructure in a pattern that does not fragment habitat corridors.
  2. Establish buffer zones around known avian habitats to minimize collision hazards
  3. Reduce impacts with appropriate turbine layout by studying daily flight patterns of birds
  4. Reduce artificial prey habitat at the base of turbines, which may in turn attract foraging raptors. Designs that minimize disturbed or unvegetated banks should be incorporated into the construction of turbine pads. Rodenticides are not recommended as a way to remove potential prey from wind sites.
  5. Avoid lighting that attracts birds and bats. Although lighting effects are poorly understood at this time, migrating song birds and bats appear to be attracted to steady burning lights. New FAA standards require synchronized flashing red lights to be mounted to the nacelle for turbines on the perimeter of the wind farm with unlighted gaps of no more than ½ mile.
  6. All electrical wires and power lines should be placed underground
  7. Avoid guyed structures as they are known to pose a serious threat to avian species
  8. Decommission non-operational turbines so they no longer present a collision hazard.
  9. Compensation can be obtained via purchase of land through fee title or purchase of conservation easements and the permanent protection of the biological resources on these lands. The land or easements should have a high biological value for the target species that have been affected by the wind energy project.

Source: Anderson, et. al, 2006

Photos from Altamont Pass

www.freelargephotos.com www.renewableenergyaccess.com BioResource Consultants. www.biologicaldiversity.org www.highton.com


Solutions specifically for the Altamont Pass Wind Farm according to an National Renewable Energy Laboratory report:

Cease the rodent control program that was applied by the County of Alameda and the wind turbine owners in 1997 • Alter habitat within 50 m of wind turbines in order to reduce prey vulnerability to raptor predation near wind turbines, thereby reducing raptor use of these areas • Move rock piles farther away from the wind turbines • Relocate wind turbines out of large drainages, and move the more isolated wind turbines closer to clusters of other wind turbines • Shut down wind turbines during the winter • Fix, replace, or remove broken or non-operational wind turbines, along with their towers • Apply the Hodos et al. blade painting scheme to the wind turbines identified as the most dangerous to raptors • Retrofit electrical distribution poles so that they comply with APLIC standards • Exclude cattle from the areas nearby tower pads of wind turbines • Purchase conservation easements to protect raptor habitat outside the APWRA as a means of offsetting the impacts that cannot be eliminated • Fund nonprofit conservation organizations with programs that benefit raptors and other bird species adversely affected by the APWRA, such as research programs or rehabilitation facilities (Smallwood and Thelander, 2005).

Some of these recommendations among others will soon be enforced since new regulation approved by the Alameda County Board of Supervisors on Jan. 11 2007 requires the wind generating companies to achieve a 50% reduction in raptor mortality.  To accomplish this the generators will take out as many as 300 turbines identified as posing an especially high risk for avian mortality.  Turbines can also be turned off during winter months, coinciding with bird migration patterns and a seasonal lull in demand for electricity.  In addition, the blades of 450 windmills will be painted in bright colors to make them more visible to the birds and latticed towers will be replaced with solid poles. Hundreds of turbines located at the end of an array of towers, which pose greater risk to hunting birds, will have their blades and generator boxes removed.  Overall, up to 155 of the highest risk turbines had to be removed within 30 days, and another 152 should be gone by Oct. 31, 2008. (O'Donnell, 2007)