This way works for the feathers of any bird. It's crucial that the feather shafts aren't broken apart; if they were, it couldn't be fixed this way.
I wish you don't have to deal with a bird in such a need of help, but you can also use this way to straighten up single feathers you find outside, if you collect them. Also, the feather may be simply held over the boiling water, the steam will work the same way.