I think you are on the right track. Most birds that I've dealt with on public land are extremely call shy. They've had every call on the market blown at them, and every hunter in the woods sets up his decoys to draw them in. It doesn't take them long to figure things out. In order to be consistently successful, sometimes you have to operate at the opposite end of the spectrum. Very passive calling, and leaving the decoys in the bag may be the trick that fills your tag every season when dealing with public land birds. Mix things up from time to time, and keep them guessing.