The cold was not to blame for more than 300 dead birds found in Yankton, although it was a suspect at first.
After sending a few of the birds to Brookings for testing, a phone call from the United States Department of Agriculture explained everything.
"Kind of like an Alfred Hitchcock," says Yankton Animal Control Officer Lisa Brasel.
Only these birds - all starlings - are dead.
"They said it was a health concern so they poisoned them," explains Brasel.
The USDA used a poison called DRC 1399 at a feedlot 10 miles south of Yankton, never expecting the birds to get so far before they died.
Some in Yankton question the government's method and motive.
"I think there's other ways they could go around besides maybe cross contaminating. I just don't think it's right," says Heather Jensen, who lives in Yankton and heard about the more than 300 dead birds.
While the birds were poisoned, they pose no health threat to humans or other animals that may eat them.
It's the method that surprised some about the downtown discovery.
"We initially thought they froze to death," says Brasel.
There may be more dead birds found in the coming days
Again they pose no health threat to humans or animals.