Mónica Guzmán, Midland Daily News
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.
[Ed: 339 times more contaminated, see below! The Midland Daily News is Dow’s home town newspaper. For facts, visit http://www.trwnews.net/]
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.
|Upstream of Dow, all is tickety-boo for the Eastern Bluebird||As for its downstream cousin? Stop! Spit that out at once!|
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.
|Earthworms collected upstream of Dow were taken as a control sample to compare toxic loads||Downstream of Dow earthworms contained 339 times more toxins, including dioxins and furans|
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.
|Wise old owls stay well upstream of Dow Chemical||Owls downstream of Dow eat 10,000% more toxins|
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.”