It's amazing what recuperative powers birds have.
A few years ago I had a hen Bulbul severely mauled by a pair that wanted the aviary to themselves. They totally scalped her to the point of death, couldn't even open her eyes. Should I just have put her out of her misery?...... no. I force fed her for two days until her eyes opened and she could feed herself. Over the next few months she not only grew back all the skin over her naked skull but also grew back all the feathers and a perfectly formed crest. I was amazed!!!!
Second story
When I was a kid I had budgies in with a pair of Eastern Rosellas. The hen Rosella ripped the whole beak off the hen budgie when fighting over a nest box. The budgie only had a round tongue poking out of an otherwise flat face (no beak at all)
Over the next couple of months, with her mate feeding her, both mandibles grew back perfectly just as a fingernail would after it has fallen off.
Any more stories like this?