The poem sets a bird's double life beside a woman's. The ovenbird is "didactic" by day, teaching in its repetitive way, but before dawn it sings something stranger and more beautiful. The schoolmarm seems to have the same split: she spends her days instructing, yet she dreams of "other people's children" and wakes sick and aching, as if something unlived is pressing on her.
Her brother mocks her, saying girdling trees is no work for a man, and she takes the ax anyway. Girdling means cutting a ring through the bark so a tree slowly dies, opening the canopy to light. She is trying to "win back the sky" from the closing-in forest. The thrush singing from a branch that hasn't "got the news" of its death is quietly sad and hopeful at once.
The mood is stubborn and a little eerie. The last image, the "bright new corset," suggests she is both freeing herself and binding something else.