I have a Western Rosella that only has one leg.... while she lived with her previous owner, her foot band got stuck in the wiring of her cage, and she ripped off her leg, her owner did not know what to do, so he decited to let nature do what it wants to do... she ended up biting off the rest of the snapped bone (up to the 'knee' joint)!!!!
And covering her own wound with the remaining skin, and she healed perfectly fine! And is still a happy little hopping birdy. So once I took her into my care, that's when I decited that I don't think I'll be using bands.... just to be safe, because I now KNOW that could really happen.