Rule of thumb would be not to buy birds from an auction. It's a shame but most people just peddle birds at those things. All mixed up with who knows what.
Years ago I was just giving away some extra layer roosters and met a guy and he flat out told me he was taking them straight to the auction to sell. I took em home. I'd rather cull birds than be part of that scene. I literally live 5 min from a place that has an auction every Tuesday. I could sell every extra bird I have if so inclined. I would rather give them away to someone who I know will take good care of them.