I may be a bit of a Vonnegut junkie (and I say a bit because I know there are some serious Vonnegut fans compared to whom I am barely considered an avid reader). Needless to say I have read numerous of Vonngeut's works (9 to be more or less exact) including Slaughterhouse-Five, God Bless You, Mr. Rosewater, and now Cat's Cradle.
In Cat's Cradle, the protagonist is in utter shock after seeing the effect of ice-nine and "dreams for a moment of dropping to the platform, of springin up from it in a breath-taking swan dive, of folding my arms, of knifing downward into a blood-warm eternity with never a splash" (260). The call of a bird-"pootee-phweet?" recalls him to reality. This questioning bird shows up in other Vonnegut books. In God Bless You Mr. Rosewater, the bird calling "Poo-tee-weet" to Eliot has a similar recalling effect. The bird call snaps Eliot out of his year long 'day dream' of sorts. In Slaughterhouse-Five, the bird calls "Poo-tee-weet?" to Billy Pilgrim as he discovers World War II in Europe is over and he stood in the abandoned silence.
This bird's call appears in all 3 books which were published within 6 years of each other. Cat's Cradle came first which is why I think the bird's call is spelled a bit differently than in the other two. Which ever way you spell it, the bird's questioning call comes during a major shift in the story, calling its attention to both the reader and the protagonist.
One of the best parts of Vonnegut is that the more of him you read, the more you pick up on in and from each book... now if only Kilgore Trout had been in the protagonist's karass...