Earle Birney's "Bushed" contains many different figures of speech (or poetic/literary devices). In regard to lines 23 and 24, one can identify personification, alliteration, and imagery.
Personification is the giving of human characteristics to non-human and non-living things. The poem is filled with examples of personification. For example, in line 25, Birney's speaker tells of the mountain sleeping.
In regard to the personification found in the line in question, one (when taking a figurative perspective) can see the cedars circling the swamps in an almost dance-like way. Not only do the trees literally circle the swamp, by providing a boundary, they circle the swamp with their movement.
Alliteration is the repetition of a consonant sound within a line of poetry. For example, in "Peter Piper picked a peck" the "p" sound is repeated.
As for the lines in question, the consonant sound of "c" illustrates the alliterative nature. Both "cedars" and "circles" both begin with "c."
Imagery depends upon the inclusion of appealing to the senses of the reader in order to allow the reader to form mental pictures of the author's work.
In regards to the poem's imagery, two very different images are expressed. First, the circling of the trees around the swamp provides a very distinct image. One can either picture the literal image or the figurative image (as defined above). The image of the antlers being thrust to the sky proves much more profound. Again, Birney challenges readers to open their minds. The antlers could refer to either literal antlers being tossed to the sky or the branches of the cedars being raised to the sky.
One other interpretation of the lines could refer to the totems the poem brings up. While their could, once again, be a literal totem (carved by the moon), there could be a figurative one as well. This adds to the overall imagery of the poem.