I don't know how else to describe it. When Mia is happy (especially when she has a toy she's chewing on) she chirps. It sounds almost like a bird. Really high pitched and kind of weird. I wish I had a video camera.
JRTs chirp. Often at ear piercingly high pitched, but not always. Dekka chirps, chatters, makes a very raccoon like noise, howls, whines, barks and screams.
Can't say that they do... They all have the normal tail wagging (or bum wagging) happy act, other then Psyche who rolls around on her back when she's happy (especially with a toy).
Izzie has one bark for alerting and general pug-assery, and then she has her chirp bark. Usually the chirp comes out when i have her Cuz ball, she's in love with it so if i don't throw it she freaks out and chirps.
She also has a sound that is more of a "Woo Woo" than a bark, she has her wookie sound too, and her other general grunts and snorts too