Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
At the beginning (and, presumably, at the end) of his poem John Shade (the poet in VN’s novel Pale Fire, 1962) calls himself “the shadow of the waxwing:”
I was the shadow of the waxwing slain
By the false azure in the windowpane;
I was the smudge of ashen fluff - and I
Lived on, flew on, in the reflected sky. (ll. 1-4)