Everytime you bring treats use your call. Some use a whistle me I use hhheeerrreee chickie chickie chickie. So I would say that when I had goodies. Now if they hear that it is like a herd of chickens coming from everywhere.
The best way is for you to be associated with food. If you feed them by hand or just simply throw a cup of grain over the fence they should start to run toward you when your out there. (I don't feed them out of a feeder)