A speaker walks into a spruce grove and notices a small sign of violence: a striped feather drifting down from a high branch, where a hawk or owl has killed and plucked a grouse. The speaker doesn't see the kill, only its leftover, and that quiet detail says a lot. Death here is ordinary, part of how the woods work, and it happens out of sight while the outer trees simply sway in the wind.
The last image shifts to the speaker's own movement. Stepping "carefully as a bridegroom" over the roots makes the forest feel like a threshold into a sacred or special place, and the roots become doorsills to be crossed with respect. The speaker seems hushed and reverent, aware of being a guest. The mood is calm and watchful, with a gentle undertone of mortality. The poem doesn't judge the killing; it just pays attention, and treats that attention as a kind of ceremony.