By the way you described it, feathers with bald spots, and a large lump, it sounds a lot like the bird I rescued when I was younger... and American Robin we named Cherry Lee. I learned a lot from helping Cherry Lee. We THOUGHT Cherry was a baby bird... turned out she wasn't, she was attacked by something, causing loss of feathers, and large bumps. We took her to the vet, and he gave her some antibiotics. We made her a HUGE cage, and took her out now and then. Even took the cage outside sometimes, so she could feel the grass. She has a diet of bread dipped in milk.. that's what the vet said to give her. You might wanna try that. I would suggest putting her in a bath tub, because it's messy. Also, her poo will stink like crazy, but if you use plastic, like you can find at Wal-Mart, or a hardware store, like Home Depot, that works wonders. We nursed her back to heath, and one day she flew away. Good luck!