I can only say for this area.. The only birds we can get to stay vocal for any length of time is the jakes. The jakes will sound off almost every time you see one. Other than that we might get a gobble while on the roost and then it stops from there on. This has not been going on just during leaf growth so I am not sure what is up with that. I watched birds from Easter Sunday on and not much luck getting them to gobble. I watch to toms battle it out on Easter Sunday while waiting for the dinner to cook. I came across them while going to check on a trail cam. The odd thing is when moose hunting if the yotes are around. You call the yotes will get howling and all that. Turkey hunting everything is silent here so it is a different year. I have tagged out so for me it is not such a big deal. Others are having the same kind of luck I had have. No answering the calls. Maybe they will once they start leaving the hens? They had only open this area up last year so I do not think it is because of pressure. I travel quite a ways to stay away from the pressure areas. With the same results nothing answering the calls. I do know a guy at work that I should be able to bump into this coming week sometime that travels half way down state and ask if he had the same results. He was on vacation as well as I was this past week.