August 22: Acorns?

I keep hearing things falling through the trees out back, and had assumed they were acorns but then I realized it was too early for acorns. They don't drop till fall, when the mast crops provide protein-rich sustenance for bears, turkeys, and deer that helps fatten them up to survive the winter. So what's making all that noise? Are the squirrels getting a head start on this year's crop, or are they knocking other things down as they fling themselves through the branches?

Random artillery in the trees--
I thought it was acorns
but it's too early.