Depending on age, this is also part of their crop, When a baby bird is being hand fed this can be seen when they are getting full, it will Fill up with formula When they're crop is empty you don't see it, once fully feathered you no longer see it either.
Nov 12, 2008
Bubbles my be ruptured air sac by: The Vet
Could be a ruptured air sac. There are other possibilities, too. You should take him in to see an avian veterinarian.
