It is easy enough to find transcriptions on the web of Ashbery's "The Dong with the Luminous Nose", even exhaustively annotated transcriptions, and one can also find a recording of Ashbery reading "To a Waterfowl", but the latter poem its text one cannot, as far as I can determine, find on the web—or rather could not, until now. It is transcribed below from volume one, issue two of Locus Solus, where it first appeared.
Moderately interesting things: that issue of LS is, the contents page declares, a "special collaborations issue". "To a Waterfowl" is the first thing listed, and the subsequent contents are listed in more or less chronological order. "More or less" because, for instance, the second-to-last item in the collaborations section is by "Uri Gagarin and William Shakespeare, arranged by Ruth Krauss"—in which case I suppose the text at hand if not all of its components was recent. I also hedge because I'm not really certain of all the dates. But: more or less. "To a Waterfowl" is the only title in the table of contents that does not have its authors listed (or, in the case of "five Chinese poets", described, presumably for reasons of length). However, the "Individual Notes on Works and Authors" at the very end of the issue states that it was "composed by John Ashbery". Ashbery says, in the recording of the reading linked above, that he only discovered after having written it (he describes himself in the recording as having written it) that the cento technique (which he calls a form) employed had any, or a long, prior existence. Also, the lineation is not always such as to keep different sources from mixing on the same line, as in the beginning of the second-to-last, longest stanza.