I agree that with the ever encreaseing amount of hunters in the woods it can`t help but make them harder to call in. but I also think genetics has something to do with it. Year after year the most vocal and aggressive birds are killed off leaving the shy, more causious birds to do a lot of the breeding. Over time I belive, these traits start to become dominent. In short, by hard hunting we are shooting some of the gobble out of our birds!