Well, I have a different perspective on on what causes the gobbling to become almost non existent. The hunting pressure does cause this problem but not because the turkeys are call shy or scared. The main reason the gobbling slows is because in the first week of the season over 50% of the birds will be harvested so most of the vocal toms are gone. The remaining toms are hened-up and a gobbler does'nt usually gobble when he has a hen in is sight, they just strut and drum. This is also what is happening when you hear roost gobbling and then silence when they hit ground. The subdominant gobblers that are left are the silent toms that come in to your calling. These birds want to breed but are afraid to gobble or even drum because of the boss gobbler. These birds hang on the edge hoping to find a hen, so hunt where the hens feed, dust, and water. Use soft feeding sounds, clucks and purr, short yelps and scratching in the leaves to try and lure these toms. Sometimes you may get a boss hen to answer you, if you do call hard and loud. Try to pick a fight with the hen, make her mad, hopefully she will come and drag the gobbler with her.