Purple finch stock still, or nearly so

This is the first purple finch seen at our feeder this winter, here for breakfast this morning. But after a few bites, along with his goldie cousin, he was nearly stock still for five minutes as they slowly looked upwards around into the trees for a hawk I couldn't see.

Apparently, they couldn't see it either. Eventually, an all-clear signal was given (and I couldn't hear that); the two flew off together.