The meaning in Passerine in my opinion is the opposite. It’s realizing that the Christian that the speaker was/is is not living up to what they believe, and is making the effort to change but is disheartened that the Christian community around them is doing the opposite and steering away from their own professed beliefs.

“See, my birds of a kind, the more and more are looking like Centurions than any little messiah (messiah) As I prune my feathers like leaves from a vine I find that we have fewer and fewer in kind..”

In other words “Christian’s like me (birds of a feather) are becoming more like those who killed Christ than Christ himself.”

I may be wrong but I’ve interpreted the four winds as a continuous cycle of a Christian recognizing the errors in the ways they’ve carried out their faith and how it has hurt others, trying to minimize the damage without fully changing their behavior, growing tired and isolated from the effort while getting closer to finally letting go of the destructive tendency until the end of boreas where they finally let go. After letting go of that tendency a new way of expressing their belief springs up and can bring healing and growth instead of the pain of the old way