Mauser06, my guess is that they will be there tomorrow, unless a big cold front moves them out. It sounds like to me that the field that you saw them flying over is in thier flight pattern. I'd guess that they are roosting on one side or feeding on one side and may have a water source in the other direction and you have found thier flight pattern. I'd go back and set up in the fence line or avaiable cover where you saw most of them moving through, and after watching awhile, you will no if you're in the right spot or not, if not move to where you are seeing them cross most often. Good Luck!