Cops mistook bird poop for cocaine on a Georgia Southern quarterback's car during an arrest last month ... and the argument over the white stuff was all caught on video.
Shai Werts -- GSU's junior starting quarterback -- was pulled over on July 31 in Clinton, South Carolina after cops say he was speeding.
During the stop, officers placed 21-year-old Werts in the back of their patrol car ... and went to search Werts' 2016 Dodge Charger.
In the video, you can see cops paying close attention to the hood of Werts' ride, shining a flashlight on the area and allegedly discovering a foreign white substance on it.