Food downstream more toxic for area songbirds

Mónica Guzmán, Midland Daily News 05/05/2006

It might look like the same trees and shrubs from a bird’s-eye view, but whether an eastern bluebird, tree swallow or house wren builds its nest upstream or downstream of The Dow Chemical Co. could mean the difference between everyday flies and earthworms and slightly more contaminated grub.

 That’s the preliminary finding of a Dow-funded study on common songbirds living on the Tittabawassee River watershed.

 The project, one of a group of contamination studies conducted by doctoral students at Michigan State University, is about one-third complete, said its lead researcher, Timothy B. Fredericks.

 But there are still plenty of measurements left to take – including tissue and behavioral data – before anything can be said about what the difference in diet means for the birds.

"They are still here, so take that as you will," said Fredericks, who presented his findings to the public at the Chippewa Nature Center Thursday. "It’s preliminary, but I’m going to say they’re OK."

His was the last installment of a four-part weekly series at the nature center about chemical contamination and local wildlife.

 Songbirds living downstream from the Dow Chemical plant ate insects and worms with up to 55 times more toxins than birds nesting upstream, the study found.

 Ninety percent of the toxins are difurans, a compound related to dioxins, Fredericks said.

Sneaking a peek at the birds’ meals was not easy. First, the researchers had to carefully extract food from wide-mouthed nestlings after mom or dad delivered the feast. Then, they had to sort out the menu of spiders, mayflies, moths and earthworms – in various stages of digestion – from more than 1,000 collected samples, and tally each item’s predetermined toxicity.

 "You learn your bugs, that’s for sure," Fredericks joked.

 Earthworms living downstream picked up the most of the soil and sediment-bound toxins of all the critters in the birds’ diet. The worms – bluebirds’ favorite snack – showed 339 times more contaminants than those further upstream. Flies were 32 times more toxic downstream, and downstream moths – the house wren’s preferred prey – had 20 times more contaminants.

 Still, the actual toxic content is at most a few hundred parts per billion, he said, and to what extent the birds are what they eat is a question that warrants more research.

 "It will be interesting to see if the tissue concentrations match up with the dietary concentrations," Fredericks said.

Testing the birds’ bodies for the presence of toxins and looking for any changes in nesting and growth are the next steps in what might be a three- or four-year project.

A similar Michigan State study presented last week found that owls are exposed to 100 times more contamination when they feed downstream of the company as when they feed upstream.

 On Thursday, Fredericks said he had no expectations coming into the study, which kept him in the field as much as 18 hours a day while he gathered data between April and August last year, tagging nearly 900 birds for future observation in the process.

 "I’ve always been attracted to birds, because they’re everywhere," said Fredericks, who is preparing for another summer of intense research. "No matter where you go, anywhere you go, you see a bird." Advertisement

©Midland Daily News 2006

Reader Comments

Friday May 05, 2006 at 02:07 PM EST Contamination 20 to 339 times more toxin downstream from Dow is "SLIGHTLY more contaiminated?"

Dale Penprase, Midland, MI

Friday May 05, 2006 at 11:33 AM EST I hope they are tracking the age of the wildlife tested. Sometimes it take several years to see effects. In the mean time, a new community has moved in. A good example might be the Eagles that recently had a webcam on their nest in British Columbia. This is the second year the eggs were infertile, and they are suggesting that the bio-accumlative effects in their diet of pesticides and heavy metals may be rendering the birds infertile as they grow older and accululate more toxins.

I had bluebirds nesting here for about 6 or 7 years, but in the past two, there haven't been any even though there are plenty of nesting boxes for them. I wonder why.

Kathy Henry Gary Henry
 


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