One of the defining characteristics of magical realism is that, since reality and fantasy and magic get all tossed together, clear morals, themes and truths are hard to identify: This is because fantasy and magic (untruth) are mixed together with reality (truth) in an inseparable way within the fiber of the text. In other words, there is no way to remove the old man's wings and still tell the same story.
One theme that appears to be represented by the climax and resolution though is that of taking metaphorical flight and having new beginnings. The conflict the old man faces seems to be coming to a close in his death, when, instead of fading into death, the old man's wings start to grow new feathers providing a climax to the story.
These feathers are strong, clean, fresh and beautiful. In the resolution, he struggles to learn to use the new feathers for flight and then...flys away, having found a new beginning while standing on the brink of death.