Lulu does this when playing, crawling on my lap or digging in blankets. It’s more of a chewing motion at these times. When wound up, it’s a beak chatter/clack, and sometimes there are little excited whistles in there. We’ve definitely gotten the fast clacking when Lu’s irritated, and other body language along with it like flat feathers, narrow eyes, and an irate vocalization “Good grief,” Hubs has been lunged at right after this. It was confusing at first, but there are always other indicators that let us know just what’s going on in that clever ‘too brain!