The poem starts with a question the speaker can't answer. A gobbling sound comes from the ridge, but is it a real turkey or a hunter imitating one? A whistle could be a factory or a train. Sounds in the landscape no longer come with clear labels, and the speaker is left guessing.
Then the poem turns to watching. The speaker tracks a vole by the trembling grass, until a breeze comes up and the grass moves everywhere, hiding the animal's path. In the final stanza the speaker imagines the weasel's side of this: the wind is its enemy, since it covers the vole's movement, and so the weasel must try to sound just like it.
The mood is quiet, curious, and a little uneasy. The speaker seems amused but also aware that in nature, and in the poem's title, disguise is a way of surviving and of hunting. Nothing is quite what it sounds like.