Two new studies released this month spotlight potential challenges with managing eagle populations in the west, reports the Wildlife Management Institute. The one study focuses on the mortality of bald and golden eagles at wind energy facilities while the other focuses on the overall population of golden eagles in the west. The findings come at a time when the federal government is considering extending eagle take permits from five to 30 years. With the current and anticipated growth of wind farms, coupled with other causes of mortality, the findings of both surveys suggest the need for continued monitoring and observation of these iconic bird species.

The first study, released in the September issue of the Journal of Raptor Research, reports that between 1997 and 2012 wind farms have killed at least 85 bald and golden eagles in 10 states, and nearly 80 percent of those deaths (67) have occurred in the last five years. The researchers only included mortality reports with unambiguous physical evidence of mortality or injury, they did not include 17 reports that were not fully substantiated (lack of physical evidence or reliable first-person source). In addition, the authors excluded the mortality of more than 60 eagles per year at California's Altamont Pass Wind Resource Area (APWRA) because that facility's mortality rates have already been documented in published scientific studies.

Their research found that eagles were reported killed at wind facilities in ten states ? California, Colorado, Iowa, Maryland, New Mexico, Oregon, Texas, Utah, Washington and Wyoming. The author's note that after the article was accepted for publication in June 2012, eagles deaths were reported in three additional states ? Idaho, Montana and Nevada. Of all the states, California (outside of APWRA) and Wyoming have had the most mortalities at 27 and 29 respectively.

"This summary likely conveys only a limited portion of eagles killed at non-APWRA wind energy facilities in the contiguous United States, considering the general lack of rigorous monitoring and reporting of eagle mortalities," the study authors write. "Thus, our finding of the reported mortalities likely underestimate, perhaps substantially, the number of eagles killed at wind facilities in the United States. Even with this limitation, we report that blade-strike mortality of eagles is geographically widespread in the United States, and both Bald Eagles and Golden Eagles are killed."

More golden eagles were killed in the spring months between March and June than during other times of the year. Also of note, very few of the mortalities reported were found during avian mortality surveys.

"More than one-half (54.1 percent) of the eagle mortalities at wind energy facilities we report were discovered by a property owner or by facility employees during routine site operations," the study states. "In contrast, less than one-fourth (18.8 percent) were found during surveys designed to document avian mortality."

At the same time, another new study published in this month's Journal of Wildlife Management found that in general golden eagles are not declining widely in the western United States, though it also reported some regional variability. The survey integrates the findings of the North American Breeding Bird Survey and the western U.S. summer golden eagle survey (WGES, conducted by Western Ecosystems Technology) and presents the methods and results while comparing the findings with other recently published estimates of golden eagle population. The study assessed populations in 12 Bird Conservation Regions (BCR's) and found that the overall golden eagle populations have been stable for the past 43 years in the western United States. There were slight declining trends in southern BCRs and slight increasing trends in northern BCRs but overall the population change across all 12 units between 1968 and 2010 was +.40 percent per year.

"Our results clarify that golden eagles are not declining, at least widely and at the present time, in the western United States, though we acknowledge occupied breeding areas may be declining locally or regionally as described by Kochert and Steenhof (2002)," the study authors write. "However, our findings do not address the question of whether golden eagles have the demographic resiliency to absorb additional mortality and maintain their stable population trajectory."

The two studies will be relevant as the U.S. Fish and Wildlife Service (Service) continues to assess a proposed rule to extend programmatic eagle take permits from five years to 30 years. The proposed rule states that the change will "facilitate the responsible development of renewable energy and other projects that will be in operation for many decades while being consistent with statutory mandates protecting eagles." It also substantially increases the fees for these programmatic permits so that the Service can recover costs for issuing and monitoring the permit over its lifetime. The rule updates regulations established in 2009 that allowed for some incidental take of bald and golden eagles under the Bald and Golden Eagle Protection Act after the bald eagle was removed from the Endangered Species List in 2007. The Frequently Asked Questions document provided by the Service cites the need for updating the 2009 regulations because the five year incidental take permits were not long enough for wind and solar companies to secure the funding, lease agreements and other necessary assurances to move forward with their projects. The proposed rule is controversial with many environmental groups as well as tribes ? the National Congress of American Indians passed a resolution at its meeting in June opposing the rule change.

The studies and proposed rule change pose a potential challenge for the agency tasked with managing eagle populations in the United States. While both studies are authored by U.S. Fish and Wildlife Service biologists, the authors of the eagle mortality study state in the Acknowledgements that the "Findings and conclusions in this article are those of the authors and do not necessarily represent the views of the U.S. Fish and Wildlife Service." In addition, a May article published by the Associated Press reported that the Service has not prosecuted wind farms for any eagle deaths, though they were unable to quantify the number of deaths when the article was published.

While populations of golden eagles may currently be stable, some are questioning if that status can be maintained. The eagle mortality authors state: "Given the projected growth in wind resource development in habitat frequented by Bald Eagles and Golden Eagles, estimation of total mortality and better understanding of factors associated with injury and death at wind facilities through robust and peer-reviewed research and monitoring should be a high priority." How that will proceed in coming years remains to be seen. (jas)