Ah!! Don't you love the way they look imploringly into Tara's camera as if to say, "Do you not SEE that BUG!? Help me get it get it get it!!"
Now why the chittery noise? No one quite knows, though it seems to be an aerial prey thing - that is, cats don't seem to make that noise at rodents. I got that juicy tidbit from Wendy Christensen's book Outwitting Cats, courtesy of Google Books; page should come up here.