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Migrating Golden Eagles Targeted By Research

January, 27, 2007

By Joe Kosack
Wildlife Conservation Education Specialist

Harrisburg, PA - The Pennsylvania Game Commission is partnering with the National Aviary, Carnegie Museum of Natural History and Lafayette College to evaluate how eastern golden eagles migrate through Pennsylvania, and identify areas of potential conflict that migrating eagles face from the developing wind energy program in the Commonwealth.

The possible increase of wind power on Appalachian ridges may threaten golden eagles as they travel their historic migratory corridor that follows these mountains through Pennsylvania to reach their nesting grounds in eastern Canada or wintering grounds in the southern reaches of the mountain chain. Since all known eastern golden eagle migratory routes track over the Appalachian Mountains, possibly along or in close proximity to ridges targeted for wind power development, the Game Commission must ensure the well-being of this state and federally-protected species - as well as other wildlife - as this growing industry sites turbines between the state's Allegheny Front and Blue or Kittatinny Ridge.

For more than two decades, the eastern golden eagle has been recognized as a geographically and genetically isolated population. That influenced its ranking as a "Pennsylvania vulnerable" species in the state Wildlife Action Plan adopted by the Game Commission and ratified by the U.S. Fish & Wildlife Service in 2006. It is not, however, a state or federally-endangered species.

"The recent increase in wind energy development projects in Pennsylvania has raised several important wildlife conservation concerns, one of which is the potential impacts to raptors which would be further pronounced during their migrations through Pennsylvania," explained Bill Capouillez, Game Commission Bureau of Wildlife Habitat Management director. "This initiative will help address that immediate concern and in conjunction with the Commission's efforts through a voluntary cooperative agreement with wind energy developers, we hope to address the remaining issues related to potential wildlife impacts. Turbine locations should ultimately be the product of a thorough wildlife impact analysis, of which migrations of golden eagles is only one part that needs to be taken into consideration."

"The Game Commission does not oppose harnessing wind power as an alternative energy source. It offers substantial environmental benefits over burning fossil fuels, reducing America's dependency on foreign oil, and hopefully making electricity more affordable for Pennsylvanians. We recognize that harnessing wind power is part of this state's and America's future. It is the world's fastest-growing energy industry. Nonetheless, the agency must ascertain what risks - both local and national - to wildlife that instate wind turbines pose, especially since impacts have been documented instate and elsewhere. It is our constitutional responsibility and a matter of public trust to safeguard wildlife."

This golden eagle study will mark the second research project sanctioned by the Game Commission to analyze the potential impact wind turbines create for some wildlife species. The first was started in 2006 when the Board of Game Commissioners approved a $153,000 State Wildlife Grant project to monitor the pre-construction and post-construction mortality of bats and birds at the proposed Penobscot Mountain Wind Farm in Luzerne County. A planned 36-turbine wind farm on the Pocono Plateau presented the opportunity to develop much needed pre-construction protocols and assessments of bat activity, measure site-specific changes in bat activity caused by wind farm development, and to correlate biological and environmental variables to the wildlife impacts.

The $25,000 State Wildlife Grant subsidizes the $177,989 eastern golden eagle telemetry study, largely funded by the National Aviary and Carnegie Museum of Natural History. Officially titled, "Assessing conservation needs of eastern golden eagles in Pennsylvania," the study will be headed by Dr. Todd Katzner, the National Aviary's director of conservation and field research. The project will chart the migration patterns of eastern golden eagles using transmitters attached to free-flying eagles - as well as individuals counting migrating eagles on ridge-tops. Researchers will trap, fit and release golden eagles with a 70-gram, solar-powered transmitter that will record their movements through GPS technology and send the information to a satellite that will, in turn, route the information to researchers.

"Using the Argos satellite system, these transmitters, once fitted on an eagle's back, will send 10 to 15 GPS locations daily," explained Katzner. "The data will be used to generate maps showing the specific route eagles take as they migrate through Pennsylvania. In addition, we'll synthesize data and observations to further understanding of eagle habitat use along migration routes."

The study also will be used to corroborate whether eagle flight behavior is influenced by changes in land topography and weather patterns.

"We're trying to get a better handle on how flight elevations and routes used by migrating eagles are influenced by topography and meteorology," Katzner said. "The information is crucial to understanding the correlation of eagle movements, landscape features and weather, and should help us determine if differently constructed wind turbines expose eagles to greater risk or provide increased protection. We are currently operating in an information void."

This past November, two golden eagles were captured near Central City and fitted with transmitters to verify the feasibility of this telemetry project. To date, the birds have been transmitting signals and their movements can be viewed at Under the SWG project up to four more eastern golden eagles will be equipped with backpack transmitters to provide movement information.

Field observations indicate that golden eagles migrating north to nesting areas in spring remain between the Allegheny Front and Kittatinny Ridge as they pass through the Commonwealth. "Their biannual passage through this 30- to 60-mile corridor provides Pennsylvania a chance to play a leading role ensuring the future eastern golden eagles," Katzner said. "We must determine if threats to their preferred habitat in this corridor will impact the population's stability in any way. This Pennsylvania pass creates a bottleneck for the population to pass through en route to breeding and wintering grounds, where the population is more broadly dispersed."

Golden eagles, which are found in mountainous areas throughout the world, are mostly seen instate during their spring and fall migrations. About the same size as a bald eagle, and sporting a wingspan that can exceed seven feet, they soar more than they flap while flying, and lack the distinctive white head that defines a mature bald eagle. Golden eagles primarily prey on medium-sized mammals.

Golden eagles are identified in Pennsylvania's new Wildlife Action Plan as a species that may be threatened by the development of ridge-top wind turbine farms or clusters. "Careful attention should be made to proper siting of turbines away from major migration pathways to minimize the risks of collision," the Plan noted. "Thorough pre- and post-construction studies are necessary to document the effect of wind turbines on golden eagles and other migrating raptors."

Dan Brauning, Game Commission Wildlife Diversity Section supervisor, said, "The National Aviary's and Carnegie Museum of Natural History's contributions to this project have created a unique opportunity to explore a relatively uncharted conservation concern. Help from two other long-standing conservation partners, Penn State University and Hawk Mountain Sanctuary, will round out this research effort. The Game Commission, the state's growing wind energy industry and Pennsylvanians surely will benefit from this research. But the biggest winners will be golden eagles.

"What this all boils down to is Pennsylvania's ridge and valley province plays an important role in the development of wind power and as a migratory corridor for eastern golden eagles," explained Brauning. "That could mean the future of this small population of eagles hinges on our ability to make responsible and informed decisions concerning the development of wind farms in this region," he noted. "But the project may also conclude there won't be a problem for eagles. Right now, eastern golden eagle numbers are stable or rising. We'd prefer to see them stay that way."

Created in 1895 as an independent state agency, the Game Commission is responsible for conserving and managing all wild birds and mammals in the Commonwealth, establishing hunting seasons and bag limits, enforcing hunting and trapping laws, and managing habitat on the 1.4 million acres of State Game Lands it has purchased over the years with hunting and furtaking license dollars to safeguard wildlife habitat. The agency also conducts numerous wildlife conservation programs for schools, civic organizations and sportsmen's clubs.

The Game Commission does not receive any general state taxpayer dollars for its annual operating budget. The agency is funded by license sales revenues; the state's share of the federal Pittman-Robertson program, which is an excise tax collected through the sale of sporting arms and ammunition; and monies from the sale of oil, gas, coal, timber and minerals derived from State Game Lands.


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