That mockingbird's "to-wee" seems to me a close relation of the birds of unspecified species quoted as "poo-tee-weet" in various Kurt Vonnegut novels, esp "Slaughterhouse 5" and "God Bless You Mr Rosewater". A-and, according to "Breakfast of Champions", Kilgore Trout's father was an ornithologist. Of course these all postdate Pale Fire James