Crazy like a crow

I've seen a lot of birds doing a lot of bizarre things. But I couldn't figure out what the heck this crow was doing. Yesterday afternoon, as I was leaving work, I saw a hooded crow (one of the common urban birds hereabouts) flying in the most bizarre bouncy way. Flap hard to climb, drop sharply, pull up, flap upward, attempt to hover, sliding from side to side, drop sharply and repeat. It weaved and bobbed 30 meters above a road full of moving cars. All I could think was that it was playing (which was surprising because crows usually play when there are other crows around to impress, and this was the only one in my line of sight). Then I noticed it had something in its beak. A small ball on a string, or something such. It repeatedly, and obviously intentionally dropped it, only to dive downward and catch it again, then regain altitude for another drop. Several times I thought the what-ever-it-was would fall on one of the moving cars, but the crow always caught it before it could fall that far. After a couple of minutes of this, the crow changed position, flying high over the broad and mostly empty sidewalk on which I stood. After a couple of false starts it dropped its cargo, which plummeted to crash in the middle of the sidewalk, in a clear area with little leaf debris and no people within 20m . As the crow came in to land, I ran over to see what the thing was. It watched me, keeping maybe 5m back, but obviously not ready to take off. The something it had carried, dropped and broken was a large chestnut, now cleanly cracked in half, with the meat easily accessible through the shattered shell.

I backed off and let the crow enjoy its well-earned meal.