I'd assumed they were bigger than that, but relooking now I have no idea why I made that assumption because there is nothing in the picture that allows you to judge scale.
I think dogwood may be correct. I haven't a picture of the foliage because there's too much of it there, |I'm not certain where they came from. Definitely not oak galls or wild strawberies.
Curiously enough our resident squirrel has been running about with something very similar. No idea where they have come from, certainly not any of the neighbours.