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.