The story of Polyphonte and her cannibal sons survives in only one source, the Metamorphoses of Antoninus Liberalis. Antoninus cites Boios' lost collection of metamorphosis myths Ornithogonia as the source of the story.
Do we know of other myths that were in the Ornithogonia?
Antoninus Liberalis, in his Metamorphoses, quote ten stories from Boios' Ornithogonia: that of Hierax, Aegypius, Anthus, Aedon, Meropis, Oenoe, Eeropus, Clinis, the story about the thieves (Phores) in the Idean cave, and, as you mentioned earlier, that of Polyphonte.
In addition, Aemilius Macer's Ornithogonia (only known from fragments) are said to be heavily based on Boios' Ornithogonia as well. Here is the relevant quote from Adrian Hollis' Fragments of Roman Poetry C.60 BC-AD 20:
Of the two major works by Aemilius Macer, we know much less about the Ornithogonia, though Ovid might have found it more useful (as a source for his Metamorphoses). It had at least two books - perhaps just two, like the Theriaca. Macer's model would have been a Greek hexameter poem of the same name (also, it seems, in two books) ascribed to one Boeus or Boeo (if the latter, perhaps the legendary Pythian priestess). This may have been composed at the beginning of the Hellenistic age, since it was known to Philochorus (F. Gr. Hist. 328 F 214, from Athenaeus 9.393e). No verbatim fragments of the Greek Ornithogonia survive - most of those adumbrated in Powell, Coll. Alex., 24-5, would be disowned by any half-decent Greek poet - but the mythographer Antoninus Liberalis (second or third century AD?) in his Metamorphoses (the 1968 Budé edition by M. Papathomopoulos is very useful) provides prose paraphrases of ten transformations into birds which are credited, by notes accompanying the text, to the Ornithogonia of Boeus.
Transformations mentioned in Macer's Ornithogonia include that of Picumnus and Cygnus.
