Stealth Mobbing of a Cooper's Hawk

This morning I went out start my car. As I headed back into my apartment building the sky was swirling with a large flock of pigeons and starlings. As they wheeled around the group focused in on a large adult female Cooper's hawk, the flock of birds spun around her and I watched as she darted over the building towards my bird feeder. She did a sneak drop down and landed in a nearby tree. The pigeons and starlings continued to circle the tree. A lone crow flew in and landed about three feet away from the hawk when it dawned on me that no one was making any noise. I had never seen silent mobbing before it was kind of pretty in a ballet kind of way to watch.

The whole scene made me think of other things I had never noticed, like I have never seen a flock of coots in flight. Oh sure, I've seen them half fly/half run across water, but I've never seen a huge migrating flock in mid air. I know they have to do this because one day the lake is empty and the next it can be filled with rafts of coots, but I've never seen the flock arrive or leave. They must be night migrants, but I've never seen it. Something to watch for, not the loftiest birding goal out there, but something I would like to see.