In just three lines, this haiku-like poem catches a small moment in the woods: a yellow-bellied sapsucker drilling into a tree. The joke, and the beauty, lies in the last line. The bird's "true name" is the one it taps out itself, not the one humans gave it. Of course, "yellow-bellied sapsucker" is the name we use, so the poem plays with the idea that the bird is somehow writing or speaking its own identity through the rhythm of its beak.
The speaker doesn't tell us how they feel, but the tone seems quietly delighted and attentive. There's a sense of listening closely and being humbled a little, as if the human labels for nature are only guesses at something the bird already knows. The mood is calm, spare and a bit playful. The short lines even mimic the stop-and-start tapping, so you can almost hear it as you read.