THE one thing I have noticed consistency with in squirrels is that when a hawk, squirrel, or yote, strolls or flies through the woods, that's when I hear the chorus of many barking squirrels. They chime in as they cruise through and move on, kind of like the wave in a stadium. I have seen it happen both ways that a few will fire off when deer come around, but also seen it get quiet. The one sure fire method is if you see a deer, there's a deer in the area.
Yes to the wave on the swooping or cruising predators.