Student's thesis renews spotted owl controversy
June 25, 2008 -- Environmentalists are acting quickly to use graduate student Heather Ishak’s research on the spotted owl to fight logging in old growth forests. Ishak’s master's thesis identified the first known instance of avian malaria in the endangered northern spotted owl, suggesting that the aggressive barred owl, which competes with spotted owls for food and habitat, is the likely carrier of the disease.
The avian malaria parasite (Plasmodium) was discovered in the blood sample from a northern spotted owl found in an Oregon forest. The finding was part of a larger study on bloodborne parasites in raptors. Ishak and her co-authors, including her thesis advisor Assistant Professor of Biology Ravinder Sehgal, found that spotted owls are heavily infected with blood parasites, more than any other owl on the West Coast. The researchers suspect that the spotted owl infected with avian malaria may have been exposed to the parasite by coming into contact with mosquitoes that fed on a barred owl, which are known to commonly carry the avian malaria parasite.
USFWS file photo
Within days of the publication of Ishak’s findings, four Oregon environmental organizations that are opposed to logging in spotted owl habitat in Elliott State Forest filed a formal notice of intent to sue the U.S. Fish and Wildlife Service to reevaluate the 1995 permit to log 22,000 acres of spotted owl habitat.
"The barred owl presents a substantial new threat to the spotted owl that was not anticipated in 1995," said Francis Eatherington, conservation director of Umpqua Watersheds, in a June 3 press release issued by the organizations that filed the notice of intent. "Continued destruction of the limited spotted owl habitat in the Elliott should stop until it can be shown that it will not further endanger the spotted owl."
According to Ishak and Oregon conservationists, the U.S. Fish and Wildlife Service's $489 million spotted owl recovery plan does not recognize or address the possibility that the barred owl might be a threat to the spotted owl's survival. The plan, which states "there is no known imminent threat to the spotted owl from disease or predation," identifies no need or methods to protect the northern spotted owl from any immunological damage due to avian malaria and other bloodborne diseases.
"Blood parasites can decrease the owl's reproductive output," Ishak said. "There is so much more to learn about how blood parasites and other potential diseases are affecting spotted owls."
Federal protection of the northern spotted owl, which was placed on the Endangered Species List in 1990, has been used as legal criteria by environmental groups to slow or stop logging in Oregon, Washington and California forests.
Heather Ishak
"The controversy has made the spotted owl one of the most intensely researched birds in the world," said Sehgal. "Prior to this discovery however, the question of which blood parasites they harbor and whether barred owls could be a source of diseases that could further limit the spotted owl's chance of survival had been largely unaddressed."
"We hope that this information will change federal officials' views on how disease and immune health of the spotted owl should be monitored," Ishak said.
In addition to Ishak and Sehgal, co-authors of the study included scientists and officials from the California Academy of Sciences, Lindsay Wildlife Museum, USDA Forest Service Pacific Southwest Research Station, Vilnius University in Lithuania, USGS Forest and Rangeland Ecosystem Science Center and the School of Veterinary Science at University of California, Davis.
Ishak's findings were presented in a paper, "Blood Parasites in Owls with Conservation Implications for the Spotted Owl (Strix occidentalis)," which was published on May 28 by PLoS One and is available online at: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0002304
The U.S. Fish and Wildlife spotted owl recovery plan is available at: http://www.fws.gov/pacific/ecoservices/endangered/recovery/pdf/NSO%20Final%20Rec%20Plan%20051408.pdf
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