What are some of the techniques used by Elizabeth Bishop to reinforce the themes of the poem "Sandpiper"?

Before we can discuss the techniques that Elizabeth Bishop uses
to reinforce her theme, we must realize her poems rarely have an easy moral or a clear
"meaning."  What Bishop's poems do have--and "The Sandpiper" is no exception--is precise
description of the physical world.   What does it all mean?  In this case, it may just mean that
we are all like the sandpiper: "preoccupied, / looking for something, something,
something." 

Both the meter and the rhyme of the poem are regular,
but not absolutely symmetrical. 

The lines of the poem are roughly
10 syllables long, but some are as short as 7 and others as long as
12.  

Some of the lines are iambic (a series of unstressed then
stressed syllables):

readability="5">

 of interrupting water comes and
goes.

Other lines, however, are
strongly trochaic (stressed then unstressed):

readability="7">

something, something,
something.

The rhyme scheme shifts
subtly from stanza to stanza.  Stanza 1 is ABCA: granted, shake, awkward, Blake.  So is stanza 3:
them, drains, runs, grains.

Stanza 2, however, is even more
symmetrical; it is a "perfect" ABAB: sheet, goes, feet, toes.  The final stanza, though,  doesn't
truly rhyme it all, unless we bend  "obsessed" to rhyme with
"amethyst."

Perhaps all this "near-symmetry" is part of Bishop's
description of nature.  It is beautiful, there are discernible patterns, but there are
also curved edges, protusions, peculiarities.  One will never cease looking for "something,
something, something."