I was just going to ask about something that may be what you are talking about. Sometimes I notice one of my girls just opening her beak-it almost looks like a person would do when trying to relieve pressure in the ears-like when landing after a flight. I was wondering if I should be worried?
They often stretch like that if they've eaten too much food or it's dry they're trying to get it down the gullet.
Sometimes I suppose it could be another issue like gapeworm or a respiratory condition, as affected birds may stretch and gape to take a breath. But I would think those would be rare conclusions to draw...
All my birds do this when they've just gorged, it's usually nothing.