These fairly common but not often seen (except during migration) eastern US forest hawks do put on a dramatic show during migration.
They migrate to Brazil in flocks, small or large, and into the hundreds on updrafts. Lifting on a updraft, then coasting down, saves lots of energy. I had a small flock of around five over my house this week. I think they were looking for a spot to roost.
Broad-winged Hawk