That depends on where you are. I've heard of guys finding baby mice in the crops of turkeys, crawfish, some earthworms, bugs etc.

I busted a 2yr old once and his crop was FULL (>1#) of lantana berries (like plump blackberries but single, not in clumps). Others have been dining on grass shoots and seeds.

What to turkeys love to eat? Hard to answer. I know turkeys love a burned area. I've seen a 70ac grass fire that was full of turkeys two weeks later. The tender shoot drew birds from all over.