This little guy has had this since he was a hatchling and I’m lost as to what to do for him. He seems healthy and active like the rest, but has this super big belly that looks like a testicle I worry it will pop or something Either way it cannot be healthy.
Does it feel soft? If you softly (be very gentle and careful) press on it does it seem to go back inside? It may be a hernia. Often they do fine with them, but there is some risk that it can become strangulated at some point, if that's what it is. Hernia's usually require surgery to fix, and birds generally are risky for surgery. If vet care is an option (I would find an avian vet for this) then they could better advise if that's what it is.