Bird symbolism in literature? I thought about that too, but wasn't quite sure what to compare them to apart from the dove of Noah's ark (the end of the flood, a sort of rebirth I suppose)... and my brain is too sluggish just right now to come up with others!! But I guess birds are often symbolically messengers of some sort, and bridges between two realms - air and land - maybe even water - so maybe between material and transcendental?
I went to look up jays and they're apparently talkative birds (don't you think it's wild what studying literature can teach you sometimes? i find out the oddest bits of information!

). Didn't see anything else that could be interesting, but I don't have a dictionary of symbols and besides maybe Montale wasn't that much into symbolism.
The birds seem really ambivalent to me as well: at the beginning they're swooping about his head, at the end they're arrows.. 'Tis strange, hum.
What do you think about "squall"? as it's of "antic fleeting swoops", he's mixing birds and water in a way - depends whether you understand squall as a cry or as rush of water or wind... interesting word.