When hundreds of dead birds were found Monday in Yankton, South Dakota, many residents were puzzled, thinking it was the latest in a string of similar mysterious mass animal deaths around the world. But this is one instance of the many where a clear cause has been identified, as the U.S. government claims responsibility for killing the more than 200 starlings.

It was initially believed that cold weather may have caused the bird deaths, but then Yankton police received a call from the USDA, attesting that they had poisoned the birds at a feedlot 10 miles away, KTIV reports. Apparently, some 5,000 of the birds were defecating in the feed meal, posing a threat to the animals and farm workers, when the USDA decided killing them would be the best action to take.

A bait laced with the poison DRC-1339 was used, though officials were surprised the birds made it so far before dying. They assure that the poisoned dead birds do not pose a risk to nearby animals or humans.

Officials don't believe any of the incidents are related, and suspect a wide range of causes to be responsible, from cold weather and fireworks to semi-truck collisions and overeating, though they admit in many instances a clear cause may never be identified. According to The AP, mass animal deaths are not a rare occurrence.

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