Mysterious happenings in the woods

Somebody - not me this time - has been having fun.

But this one puzzled me.

Fortunately I had an instant answer from a passing student. He is doing his dissertation on how birds feed, from which angles they approach their food, and he was leaving these tasty bites up even when he wasn't there to get the birds used to the target.

And as for me, well, I wanted to prove how hard it is to catch a falling leaf ...

Music: Lucky Day by RogerThat