Most birds have 9 air sacs which are located on both sides of the body starting at about the ‘shoulder' (under the wing) area down to the area at both sides of the lower abdomen.
A very complex respiratory system in birds is what aids in their ability to fly. They actually have pretty small lungs that also work very differently than ours, making them very susceptible to toxins in the air that we may not even know are there.
Sometimes an air sac ruptures and the air escapes into the surrounding area causing what feels like a cyst or ‘bubble'. These often occur on the back of the neck where the air bubble tends to rise; however, under the wings or at the middle of the back to one side of the center and in the area where the tail feathers begin, to either side of the vent or on top, may also be involved.
This air pocket will enlarge and can cause some discomfort and other complications, including subcutaneous emphysema, if not relieved. You must get to your vet (or find any vet comfortable with treating avians and go). Usually they will, under very sterile conditions, insert a needle to release the air and then, in some cases, effect surgical repair. In all cases an antibiotic follow up is necessary. This might be something they deliver themselves or a prescription they give you (or both). If it's a Rx given to you, be sure to give it until it's all gone. Never stop it early without specific instructions by your caregiver.
Some birds will have this problem recurrently, others will have it once and never again. Underlying causations are frequently never identified, but nevertheless, it's something you must be sure of.
Good luck with him - and very good job at catching this early . Much better chance of uncomplicated recovery.
Certified Avian Specialist
Cert. Avian Specialist; Int. Assoc.Animal Behavior Consult; Pet Ind. Joint Advisory Council; author
It's not so much surgery as letting the air out.
If this is what it is and from your description it sounds like it. As soon as you said "full of air..." (or liquid) it's what came to mind.
The antibiotic at this point probabl won't hurt (though I'm not fond of administering without knowing for sure there's a bacterial infection) - but you really need to have a professional diagnose the actual problem and do the initial release of pressure. That way you'll learn how to do it yourself without chancing injury to something else.
Many people go lifetimes without ever seeing this. When I was a kid, oh so many decades ago, when one of our chickens would present with this - she was Sunday dinner. It has a habit of recurring
Find an avian vet near you http://aav.org/vet-lookup and
http://veccs.org/hospital_directory.php
These days, with birds growing fast in popularity - many DVM's are quite experienced and able to see and treat many birds. If you have a supply store that sells birds or know of any bird breeders - ask them who they use for their bird care.
To be sure the vet is a good one, make sure you're there for the exam. This should include hands on, feeling the chest area, peering into the mouth with a well placed flashlight and lifting the tail feathers to examine the vent.
This exam should also include any one or more of the following: Blood tests, gram stains/cultures, x-rays, even oral/crop/tracheal swabs and so on.
If the examining vet doesn't perform a hands on exam, or worse, leaves your bird in their cage or carrier, leave immediately. This is not the vet for you or your bird.