Mike Marcus: "Near the start of Part I, Chapter 8 of ADA, Van and Ada are encouraged to fraternize, as it were: "...and under the pretext of picking up a fir cone he disengaged his hand. He threw the cone at a woman of marble bending over a stamnos but only managed to frighten a bird that perched on the brim of her broken jar. “There is nothing more banal in the world,” said Ada, “than pitching stones at a hawfinch.“ [snip] Firstly, an allusion to / parody of a famous phrase in Hamlet, who is feigning madness:"I am but mad north-north-west. When the wind is southerly, I know a hawk from a handsaw." Handsaw means heron.Nabokov has "hawfinch ....... who knows a cone from a stone"....  He mentions B.Boyd, and D.B. Johnson (2000): "Percy de Prey in ADA was assigned the identical epithet, coeur de boeuf, so he too was Vere:"

Jansy Mello:  The sentences Mike Marcus selected, reminded me of another episode, directly related to Percy de Prey. 

I didn't find, right now, the threads that once led me from one paragraph, or a selection of images, to the other  I think they may be found in A.Sklyarenko's "Ada's Triple Dream."  

There are several elements in common between the episodes, such as the holograph dream-quality of doubles and twins, a reference to birds... Perhaps the items below will be helpful and add some information to what Mike Marcus has been searching, in connection to Shakespeare (athough I cannot follow most of his associations...).I'm curious about what will come out from this sampling...

ADA:
(1) "‘I’m not interested. Now comes a little boy.’/ ‘Zdraste, Ivan Dementievich,’ said Van, greeting his fourteen-year-old self, shirtless, in shorts, aiming a conical missile at the marble fore-image of a Crimean girl doomed to offer an everlasting draught of marble water to a dying marine from her bullet-chipped jar [   ] Ah, the famous first finch./‘No, that’s a kitayskaya punochka (Chinese Wall Bunting). It has settled on the threshold of a basement door. The door is ajar. There are garden tools and croquet mallets inside. You remember how many exotic, alpine and polar, animals mixed with ordinary ones in our region.’

(2) "Percy, you were to die very soon — and not from that pellet in your fat leg, on the turf of a Crimean ravine...you were to die very soon, Percy; but that July day in Ladore County, lolling under the pines, royally drunk after some earlier festivity, with lust in your heart and a sticky glass in your strong blond-haired hand...Burly, handsome, indolent and ferocious, a crack Rugger player, a cracker of country girls, you combined the charm of the off-duty athlete with the engaging drawl of a fashionable ass.[   ] ‘In a birdhouse fixed to that pine trunk,’ said Marina to her young admirer, ‘there was once a "telephone." [  ] They thought, he thought, he was a shepherd too."

(3) "Maidenhair. Idiot! Percy boy might have been buried by now! Maidenhair. Thus named because of the huge spreading Chinese tree at the end of the platform....N’est vert, n’est vert, n’est vert. L’arbre aux quarante écus d’or... Ginkgo, gingko, ink, inkog. Known also as Salisbury’s adiantofolia, Ada’s infolio, poor Salisburia: sunk; poor Stream of Consciousness..."

(4) "Young Fraser, who has just been flown back from Yalta, saw Percy killed on the second day of the invasion...He will tell you the whole story himself, it accumulates more and more dreadful details with every telling [   ] (Bill Fraser, the son of Judge Fraser, of Wellington, witnessed Lieutenant de Prey’s end from a blessed ditch overgrown with cornel and medlar, but, of course, could do nothing to help the leader of his platoon [   ] Percy had been shot in the thigh during a skirmish with Khazar guerillas in a ravine [   ] Loss of blood caused him to faint, as we fainted, too, as soon as he started to crawl or rather squirm toward the shelter of the oak scrub and spiny bushes, where another casualty was resting comfortably [   ] A smiling old Tartar, incongruously but somehow assuagingly wearing American blue-jeans with his beshmet, was squatting by his side[   ]‘Karasho, karasho ne bol’no (good, good),’ said the kindly old man and, picking up the automatic pistol which Percy had dropped, he examined it with naive pleasure and then shot him in the temple [   ]One supposes it might have been a kind of suite for flute, a series of ‘movements’ such as, say: I’m alive — who’s that? — civilian — sympathy — thirsty — daughter with pitcher — that’s my damned gun — don’t... et cetera or rather no cetera... while Broken-Arm Bill prayed his Roman deity in a frenzy of fear for the Tartar to finish his job and go. But, of course, an invaluable detail in that strip of thought would have been — perhaps, next to the pitcher peri — a glint, a shadow, a stab of Ardis.) / /‘How strange, how strange,’ murmured Van when Cordula had finished her much less elaborate version of the report Van later got from Bill Fraser./What a strange coincidence! Either Ada’s lethal shafts were at work, or he, Van, had somehow managed to dispatch her two wretched lovers in a duel with a dummy."

The word "peri" appears twice.  Here is another quote and Brian Boyd's explanation in Ada Online:

(5) "Marina, with perverse vainglory, used to affirm in bed that Demon’s senses must have been influenced by a queer sort of ‘incestuous’ (whatever that term means) pleasure (in the sense of the French plaisir, which works up a lot of supplementary spinal vibrato), when he fondled, and savored, and delicately parted and defiled, in unmentionable but fascinating ways, flesh (une chair) that was both that of his wife and that of his mistress, the blended and brightened charms of twin peris, an Aquamarina both single and double, a mirage in an emirate, a germinate gem, an orgy of epithelial alliterations."