The poem catches a quiet, strange moment: birds passing over a city after dark, heard but not seen. The title, "Flight calls," points to the sounds migrating birds make as they travel at night, and the speaker seems to be listening upward, half-startled by what drifts overhead.
The first three lines pile up bold, almost violent images. The unseen flyers become "dark fire," "a holy rocket," "a cut-throat god." They feel awesome and a little dangerous, something larger than the streets below. Then the tone shifts. The last three lines turn to a starling's songs, which "come to town / for an evening out," as if the bird were a cheerful visitor dressing up for a night on the town.
The contrast gives the poem its charm. Wonder and menace sit beside playfulness, and the mood is hushed, curious and a bit humorous. The speaker seems to find the wild both sacred and delightfully ordinary.