Jerry Friedman: The first reason
that comes to my mind for having Shade's father die is to have a literal
referent for the waxwing slain (and another place for Kinbote to be
belated).
JM: VN scholarship often connects the
waxwing slain to a not so distant event: VN's father assassination in
Berlin.
There is a (possible) premonitory vision of its
"ashen fluff", in relation to a gun and a
humming-bird, in Lolita: "We must remember
that a pistol is the Freudian symbol of the Ur-father's central forelimb [...]
Farlow, with whom I had roamed those remote
woods, was an admirable marksman, and with his .38 actually managed to hit a
hummingbird, though I must say not much of it could be retrieved for proof —
only a little iridescent fluff."