The speaker imagines her spirit as a caged bird, beating against its bars all day. The bird is not literal—it is her inner life struggling against whatever confines it. The winging strength is “whirred vainly away”: not just stopped, but spent uselessly, like an engine spinning with no result. That creates a mood of restless, claustrophobic frustration. She wants to move, to escape, but cannot.
At night, something shifts. The bars blur, yet instead of feeling free, she feels small. Looking at the stars, she understands her own impotence: what good are wings, she asks, before such enormous distance? Wings seem almost rude or ridiculous, a tiny claim to freedom that the universe ignores. The mood becomes quieter and lonelier, full of longing and resigned awareness. The struggle has drained away, leaving only the truth of being trapped and tiny under the sky. There is no easy hope here, only a kind of night-time clarity.