In just three lines, this haiku-like poem sets a quiet scene: a field that is no longer a field, and a ruffed grouse making a sound where nothing seems to be. The word "former" suggests the land has changed, perhaps grown over with brush or young trees, or simply been left behind by whoever once worked it. Into that emptiness comes the bird's drumming, which the poem describes as a drum made "out of thin air."
That phrase works in two ways. A grouse really does beat its wings against the air to produce a low, thumping sound, so the image is literal. But it also hints at something almost magical, as if life can make an instrument from nothing at all.
The speaker doesn't announce a feeling. Instead, the mood comes through the listening: stillness, a little loss in "former," and a small surprise at nature's persistence. The poem feels hushed and attentive, and it leaves us with the sense that abandoned places are never really silent.