Thanks, Airedale1, I see that they are not all red tailed hawks in the photo. Not sure that all in the group that we saw were red tailed, we were too surprised to be good observers. A "boil" is a good term for what we saw.
Here is a video of a kettle of broad winged hawks, comparable in numbers of birds to what we saw:
https://www.youtube.com/watch?v=VJTBnN1FTb0