Fog makes the world small, and these four short scenes stay close to what's right in front of the speaker. On a porch, two blowflies mate on a knee, a blunt, funny detail that treats the human body as just another surface in the natural world. Then attention narrows even further to a single red branch, the one thing the speaker can focus on while everything else blurs.
The third scene is quieter. Counting bird songs to notice which are missing suggests a listener who knows this place well, and the poem hints at a small worry about absence, though it never says so outright. The last take lets the sun break through, and the trees' shadows stretch only halfway to the ground, as if the light isn't quite finished arriving.
The mood is patient, curious and a little uncertain. The speaker doesn't try to explain anything, just watches and listens, and the fog becomes a way of paying closer attention.