In norhtern and west-central IL the bucks are still in small groops and have not seperated yet. I think that will start to happen within the next week. I suspect we will start seeing them start chasing does as soon as that happens. As drstalker said, there isn't a lot of corn out in the northern areas and until that happens, the bucks usualy stay put and limit their movements to night around here.
Good luck and be safe