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As many as 7,000 mallards have died in a small pond near Pierre, S.D., apparently from an infection stemming from eating moldy grain. The birds were found Jan. 30. The pond is kept open by a well “with no obvious way to shut it off,’’ one wildlife official said.

S.D. Game Fish and Parks Department, Star Tribune

Thousands of mallards die; traced to eating moldy grain

  • February 9, 2011 - 11:57 AM

As many as 7,000 mallards have died in a small pond near Pierre, S.D., the apparent result of the birds ingesting moldy grain from a feedlot.

The congregation of mallards had remained in South Dakota despite severe cold and snow this winter, gathering in a small pond, apparently kept open by an artesian well.

The well can't be easily shut off, according to a U.S. Fish and Wildlife Service memo.

The fear at first was that the birds died of cholera. Instead, toxicology reports indicate a fungal infection as the cause, likely caused by the moldy grain.

The service was concerned that an eagle die-off might also occur in the area because the big birds -- hundreds had been wintering there -- were seen feasting on the dead ducks.

The die-off was in western Sully County, not far from Lake Oahe.

A Fish and Wildlife Service crew, along with workers from the South Dakota Game Fish and Parks Department, recovered the birds, placed them 20 to a bag and double-bagged them before loading them onto flat-bed trailers.

A sample of the birds was sent to a national wildlife laboratory, which determined the cause of infection and death.

The mallard die-off is one of the largest of its kind that wildlife officials can recall. Hearty birds, many mallards will stay north in winter, almost no matter the weather, if they have food and open water.

DENNIS ANDERSON

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