There are a few reasons why there is more gobbling in the mornings than in the evenings.
First, they have been sitting there mostly tight lipped all night. Holding in all that testastorone wears on them. Second, they gobble to attempt to call hens to them. The more hens the more fun they will have. Almost ALL mating takes place in the morning until mid-day. Third, domanince, they gobble to set a pecking order.
At about mid-day most if not all hens are setting on the nest, gobblers then go into a feeding mode. They will attempt to regain energy for the next day. They will still gobble and can be worked quite well at this time and you don`t have to contend with all those hens. A hour or so before fly up some birds will re-group to go to roost. Remember there is safety in numbers. Gobblers with hens or another gobbler for company don`t need to gobble due to the fact that the hens aren`t coming to them. They are already there or are going to roost themselves. You can at times get them to shock gobble in the evenings but it`s a little harder.
Took my nefhew out last year on youth day. Found an area torn up. Set down 1 hour before fly up. I hit every locator at fly up time but got no reply. But with that much sign I couldn`t walk away. The next morning at dawn 8 birds gobbled only 200 yards away. GO FIGURE.
And yes, he got his fisrt bird
'Lord, hold our troops in your loving hands. Protect them as they protect us. Bless them and their families for the selfless acts they perform for us in our time of need. Amen..'