Mass Die-Off Of East Idaho Birds Blamed On Disease And Poison

Jul 1, 2015

When more than 2,000 migrating snow geese were found dead at eastern Idaho’s Mud Lake in March, headlines all over the country said the birds had fallen dead from the sky. Idaho’s Department of Fish and Game says that did not actually happen, but the agency has revised its explanation of what did occur.

When the birds were found, fish and game biologists saw clear signs of avian cholera. And the department initially ascribed the whole die-off to cholera.

But as agency workers disposed of the bodies they saw some with no signs of the disease. They performed necropsies on some of the birds and concluded some died from cholera and others from poison. Idaho Fish and Game’s migratory bird coordinator Jeff Knetter, says it was probably a common rodent poison used by farmers. Snow geese often forage in agricultural fields.

If it had just been cholera, Knetter wouldn’t be worried. The disease is common among snow geese and large die-offs like this one aren’t considered unusual. But Knetter says he hasn’t heard of so many migratory birds being killed by poison.

“Certainly not in Idaho and it’s tough for me to speak beyond the borders of the state but I do have colleagues up and down the Pacific Flyway and I’m not familiar with any other instances like this,” he says.

Knetter says Fish and Game could not examine enough of the birds to know how many had cholera and how many were poisoned. He doesn’t know why this poison would have killed birds this year and not in the past.

Knetter speculates this incident was just a matter of timing. Maybe, he says, the birds and the poison arrived in fields a little too close together.

“I’m a little bit concerned about it,” Knetter says. “We’ll certainly be vigilant in the future. This sort of is another tool in the toolbox, another thing to consider when we come across any sick or dying waterfowl.”

Knetter says he’s not very worried about future problems with agricultural poison because as a species, snow geese are doing very well. 

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