In the extract that I assume you are referring to, Bruce Chatwin narrates a harrowing voyage taken in 1593 that was similar in some respects to the voyage in "The Rime of the Ancient Mariner." Some argue in fact that this voyage inspired the poem by Coleridge. The ship of John Davis was separated from the others in his fleet and sailed to Penguin Island close to the tip of South America. There, the crew wantonly slaughtered thousands of birds. The birds, however, took their revenge through a "worm" that the bodies carried which nearly destroyed the ship and killed almost everyone on board.
This rather repugnant story mirrors many of the key themes of "The Rime of the Ancient Mariner," mainly in that both stories narrate an act of brutal destruction of nature and an apparent punishment that occurs as a result. However, it is important to note that in the poem, the Mariner kills on a whim, for no apparent reason, whereas it is clear that the sailors in the extract kill systematically and with intent for food. Likewise we can compare the worm in the dead birds to the Polar Spirit of the poem. Both of them are responsible for the revenge or punishment of the people that acted against Nature, but obviously the worm is a natural phenomenon and has no intelligence or feeling, whereas the Polar Spirit in the poem is presented as a supernatural force which wills its actions.