If you use the lightbox you can see that those black bits are birds: starlings, in fact. Two days ago I went out on the porch and heard that squeaky rusty windchime sound they make when they're migrating/feeding. The sound, while not deafening, was loud enough to get my attention. I walked down into the field and could see them inside the woods, moving west to east, the back group flying over the crowd to become the front feeders. It's a marvelous way to keep the flock moving foward and no one starves.
Some of them landed on the field just outside the woods, and when they took off it was like the shock wave sound you get when a bomb goes off elsewhere. Yesterday we had three new batches, this time flying above the trees as well as inside them, and the sound when they all landed and then took off truly had a reverb. Im guessing this group was maybe a thousand or so, the later groups might have been three times that. this is the first time in maybe twenty years that we've seen them.