Thanks for that!
By air sac do you mean the crop or the lung?
I have noticed that from the start when Bo does a couple of laps of the lounge room and lands on my shoulder he wheezes like a person who has smoked umpteen cigarettes every day until he gets his breath back - have always joked that he is too unfit to survive in the Australian wilds because he couldn't keep up with the rest of the flock if he was out there!
I gather that this is not a self-healing problem??
Been thinking about your comment that the air needs to be released so I don't know whether it was clear to you that the bulge only appears when he is talking and disappears when he stops (and is more evident on the pronunciation of some words), much like a trumpet player's cheeks.
Still monitoring as it only appears when Bo makes one particular noise which is like a crow "Caw, caw" and not during his other speech patterns; otherwise he is bright and bubbly!