Had to re-encounter Bishop after about 10 years for a class, the poems and prose. Never having been a fan of the poems, it was interesting to note that I enjoyed the prose a fair amount. Bishop is most effective when she is afforeded the time to develop the emotional weight of the recollections she deals in. By means of explicit description and the rhythm of the narrative, she is able to charge the descriptions with the intimacy she wants to instill the reader. In the poems, she has less space to do this, consequently, the lines must bear too much weight.
What in the prose comes across as tenacious recollection in the poems gives a sense instead of rote nostalgia. The prose feels more "improvisational" than the meticulously wrought poems. The poems feel clinical in their crystalline order. E.g. "Sestina" is artfully constructed--putting forth a seamless narrative in the mold of what is essentially a lyric form--best at announcing its own artifice. Many poets use the sestina to convey the obsessive character of intense recollection--to my mind this is a misapplication of the form as the real character of memory belies the conscious manipulation of a form like the sestina. The narrative quality in "Sestina" is a kind of artifice, but the evident charade seems to run counter to the poet's evident desire to express "the truth as it was."
To my mind, poetry is the messenger of forgetfulness, absolution and the plasticity of the conscious mind and the resulting plasticity of recollection. I do not believe in truth or nostaglia. This seems to run counter to the epic tradition, however, to which poets like Bishop are most closely aligned.
It appears necessary to identify two governing impetuses for poems: those that are primarily narrative (agents of memory) and those that are primarily lyric (agents of forgetting). The Styx and the Lethe. It is perhaps a subjective judgment to state that poetry's most native role is the latter, however. Under close scrutiny the entire dichotomy breaks down--as in the Chinese tradition where there is no prose/poetry duality--merely specific terms for specific kinds of writing with a certain style of representing (or not representing).
In this light, the category of "prose poem" becomes much more broad--referring not only to poems without arbitrary linebreaks, but also to those which represent mimetically like prose does, that tell a story in "realtime"--the elegiac narrative tradition (Silliman's Quietude)--which has become the measure against which verse has been compared for the past 40 years or so, most likely since the New Critics and the Confessionals. (Doctor and Patient).