I have recently returned from Austin, Texas, where there are lots of bats and grackles.
The common grackle is a slim, blue-purple Icterid, with a fanned tail and yellow eyes. At dusk, certain trees in car parks (there are more of them than parks) sound like electricity, as if made from light-bulbs or an electric fence. The low buzz comes from a group of grackles, always difficult to see in the branches. So the sound is bodiless.
In mid-summer, 1.5 million Mexican free-tailed bats sleep under the sheer, pale Congress Bridge across the Colorado River, which locals call Town Lake. When I was there, just a few bats had yet come back from Mexico, where they winter. Black spots against grey, solitary bats are tricks of dusk: a part of the failing light rather than an animal. You never get a good look at them. They made the city feel expectant.
The grackle-tree and first few bats are delightful and unnerving. Noisy and alive and always to some degree hidden, out of shot. Right on the edge of what you can know by looking and listening.