The U.S. Geological Survey, in collaboration with the U.S. Fish and Wildlife Service, has released a study that will enable ecologists, managers, policy makers, and industry to predict the bird fatalities at a wind facility prior to it being constructed.
The study examined golden eagles as a case study because they are susceptible to collisions with wind turbines in part because of their soaring and hunting behavior.
Bird fatalities due to collisions with rotating turbine blades are a leading concern for wildlife and wind facility managers. This new model builds upon previous approaches by directly acknowledging uncertainty inherent in predicting these fatalities. Furthermore, the computer code provided makes it possible for other researchers and managers to readily apply the model to their own data.
The model looks at only three parameters: hazardous footprint, bird exposure to turbines and collision probability. “This simplicity is part of what makes the model accessible to others,” said Leslie New, assistant professor of statistics at Washington State University, who led the research project as a USGS postdoctoral fellow. “It also allows wind facility developers to consider ways to reduce bird fatalities without having to collect a complicated set of data.”
High rates of bird fatalities do not occur at every wind facility. The geographic location, local topographic features, the bird species and its life history, as well as other factors all play a role in the number of fatalities.
Taking advantage of publically available information, research scientists incorporated a wealth of biological knowledge into their model to improve fatality predictions.
“Uncertainty in this model can be reduced once data on the actual number of fatalities are available at an operational wind facility,” said New.
To establish the utility of their approach, the scientists applied their model to golden eagles at a Wyoming wind facility. Their long-life span combined with delayed reproduction and small brood size means that there are potential population-level effects of this additional source of mortality.
Golden eagles are protected under the Bald and Golden Eagle Protection Act and the Migratory Bird Treaty Act. The combination of law, conservation concerns, and renewable-energy development led the USFWS to develop a permitting process for wind facilities. The USFWS permitting process requires that fatality predictions be made in advance of a wind facility’s construction. This allows the facility’s impact to be assessed and any mitigation measures related to turbine placement on the landscape to be taken. The new model was developed specifically for the purpose of assessing take as part of the preconstruction permitting process.
The study supports a conservative approach and the researchers’ model is used to inform this permitting process and balance management of eagle fatalities.
The article, “A collision risk model to predict avian fatalities at wind facilities: an example using golden eagles, Aquila chrysaetos” by L.F. New, E. Bjerre, B. Millsap, M. Otto and M. Runge, is available in PLOS ONE online.
About the Golden Eagle:
The golden eagle has a vast range, from the tundra through grassland, forested habitat and woodland brushland south to arid deserts including Death Valley, California. They are aerial predators that build nests on cliffs or in the largest trees of forested stands that often afford an unobstructed view of the surrounding habitat.