What initially looked like an addition to the mysterious deaths of hundreds of birds across the country, is no longer a mystery.

The USDA has come forward and admitted that they poisoned the birds due to agricultural concerns.

From KTIV:

They say that they had poisoned the birds about ten miles south of Yankton and they were surprised they came to Yankton like they did and died in our park,” says Yankton Animal Control Officer Lisa Brasel.

The USDA confirms the story, saying the deaths were part of a large killing at a private feed lot in Nebraska.

They say a local farmer had been having troubles with about 5,000 starlings defecating in his feed meal. Department of Ag officials say because of health concerns for the farmer’s animals and staff they decided to kill the birds.

They used a bait laced with the poison DRC-1339. The USDA says the birds ate the bait then flew back to Yankton and died.