This is a very difficult case in that you have no one local to call upon for assistance. Unless the mass is actually observed (in person), it is difficult to make a diagnosis. The mass could be of no consequence, an abscess or even a possible tumor. Without taking a biopsy or seeing if it is an abscess and diagnosing which bacteria is involved, the use of an antibiotic may not be prudent. She may need a specific type of antibiotic or a broad spectrum like Baytril.

If you cannot find a local veterinarian or wildlife entity that will help you, we would suggest that you go online to a wildlife rehabilitation center/poultry or goose farm. See if they might have seen anything like this before. Poultry farmers and other such specialists see common anomalies and may have seen something like this before. If so, they may be able to tell you what your next move might be and even provide a treatment protocol for you. Sometimes, the local poultry/goose farmer can offer a treatment as they may use various antibiotics, know the dosage protocols as well as be able to estimate weights for dosage purposes. We hope this information helps, but not having seen the mass, it would not be prudent to offer any course of treatment as it could be more detrimental than the problem itself. Please let us know how this situation progresses. The Regal Swan