At first glance, these three short lines catch a fleeting moment: a vast flock—perhaps a million starlings—streaming south as evening arrives. The speaker doesn’t describe the birds in close detail, only the effect they create. Together they seem to pull the final shade of night across the sky, as though the flock itself is drawing darkness down over the landscape. The image feels enormous and strangely quiet at once.
The mood is one of awe mixed with a gentle ache. “Last shade” suggests an ending, and “heading south” hints at departure, migration, and the turning season. Watching so many lives move as one can feel both thrilling and a little lonely. The speaker stands back, not explaining, just letting the dark arrive and letting the starlings carry it with them.