Dioxin up in owls downstream
04/28/2006
Cheryl Wade , Midland Daily News

A dioxin study of the great horned owl in the Tittabawassee River watershed shows the birds are exposed to 100 times more contamination when they feed downstream of The Dow Chemical Co. as when they feed upstream in areas presumed not to have contamination.

However, it's still unclear what, if any, effect the dioxin has on the owls.

Sarah Coefield, a Michigan State University biologist, is studying the large nocturnal bird as part of a group of projects to determine dioxin levels in creatures that live in or near the river. She presented her early findings at the Chippewa Nature Center Thursday. Hers was the third in a four-part series the center is sponsoring to help locals understand how chemical contamination affects wildlife.

The study began in 2003 and Coefield will continue the research through 2008. The Dow Chemical Co. is paying for the MSU study.

Coefield said she looked at the owl because it eats a variety of animals: mice, rats, rabbits, voles, ducks and just about anything it can take down. In addition, birds are more sensitive to chemicals than many other types of animals, she said. The owls eat the meat of their prey and regurgitate the parts they can't use. That material, which comes out as pellets, is what Coefield studies. Not only will the work reveal information about the owl, but also about the smaller animals it eats.

Coefield also is studying the owls' tissue health as determined by blood samples, their overall health and reproductivity. She said she doesn't "have all the numbers crunched" yet but said based on her observation, the owls seem healthy. Owls normally are found at the rate of about one per square mile, and Coefield has found owls in appropriate numbers during the study.

"There were twins in every nest this year" in both study areas, she said. "That's normal."

The studies include terrestrial species such as the owl because there's an interplay between the sediment and the soil when the river floods, Coefield said.

Because owls are nocturnal, she did much of her work from dark until dawn.

"We have gotten very good at canoeing in the dark," she said. "Sometimes they'll actually come to the canoe and hoot at us."

Study methods didn't hurt the bird, Coefield said. Some owls had their tails banded with tiny radio transmitters. Some were briefly caught in fine "mist nets" and then released. Researchers also made nests for the owls and fixed them high in trees, and the owls seemed to like them, she said.
 


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