Saw a post, can't find it now, from someone who did some surgery on a wing mass. I would urge anyone finding such a mass to investigate feather cysts in canaries. Certain show canaries have been overbred to produce soft feathers, and they develop the inability to express the feathers properly The feathers develop instead like an ingrown hair, growing under the skin. Eventually they form a hard mass under the skin. (An unpleasant smell when opened up) They can be removed surgically, but frequently will return. They look exactly like the photos in the entry that I read. Such birds should never be bred since the affliction is hereditary