The poem opens with a cry of breakage: "Broken broken broken / my high gray room." The speaker seems to be mourning the loss of a shelter, and the questions that follow ("How did it happen?", "Who made off with...") have the dazed feeling of someone surveying damage. The "sudden searing roots" suggest something torn out violently, and the odd line about being shown "how it feels to belong" reads as bitter, as if belonging is only understood once it's taken away.
Then the poem turns to a hermit thrush and its bog, which sits where a glacier-like "castle of ice" melted thousands of years ago. The scale shifts from one person's loss to deep time. Judging by the imagery, the "latter-day invaders" and their "jagged ladders" may be people or their structures, now left to woodpeckers. The "empty nets" preserved in tannic water end the poem quietly. The mood is grief, steadied by a long, patient view of the landscape.