Another Oak Eating Year
Periodically, the local oaks are heavily infested with these leaf-munching caterpillars, which can almost completely denude a tree.
Some of the hapless critters fall off the tree and crawl around aimlessly, presumably to starve. Or perhaps they are done eating and ready to find a nice spot to cocoon. The oak tree above looked quite weak at a time when it should be showing vigorous new (tasty) leaves.