The appearance of the gaggle of pole -- jackdaws, or grey crows (cornacchie grige) - in Paradiso 21 is a strangely unsolemn moment in an otherwise almost forbiddingly sober canto. Jackaws are usually not associated with contemplation - and the variously active groups of birds described in the simile seem busy, but not intent upon higher things:
And as accordant with their natural custom
The rooks together at the break of day
Bestir themselves to warm their feathers cold;
Then some of them fly off without return,
Others come back to where they started from,
And others, wheeling round, still keep at home;
Such fashion it appeared to me was thereRobert Hollander notes that these birds have "black wings, silver eyes, and large red beaks encircled by yellow," and adds that according to Benvenuto, they love solitude and choose the desert for their habitation.
Within the sparkling that together came, (21:34-41)
Thanks to Dren, we now know our black birds have a holiday tie-in, via Ovid, no less. He shared this piece from the Washington Post that offers a bit of philological archaeology. It turns out that while we all sing "four calling birds," during the Twelve Days of Christmas, the original line involved "coally birds," an adjective derived from, and sounding like, "coal."
The OED finds the word in Golding's translation of Ovid's Metamorphoses - the tale of Coronis and the raven who told Apollo of her infidelity.
As thou thou prating Raven white by nature being bred,Indeed, we might have Ovid to thank for Golding's bringing the word into print, and giving it the opportunity to be mistaken for "calling birds," thus helping perpetuate the derangement of language which happens to be a prominent theme in the second book of the Metamorphoses. (See, for example, here.)
Hadst on thy fethers justly late a coly colour spred.