Yesterday I found a finch (adult female) unable to properly fly but otherwise appearing healthy, I kept her on the porch for safety and monitoring, and this morning she had a large air bubble, approximately the size of her skull, on the back left of her neck. This evening the bubble had expanded so bare skin is visible on the right as well, and when i picked her up for closer examination i could feel that the underside of her chest is now essentially one large bubble. She is still active, eating and chirping, though her left wing has been steadily pushed further and further from its normal resting position over the course of the day. I haven't been able to find much info about when to treat or not treat this, and while I'd like to get her flying back to her mate asap, there is of course a risk of infection if I puncture the skin to let the air out. I also cannot be sure if the difficulty flying has another cause, in which case she would need time for her wing to heal anyway. Picture is from this morning.