Symbols are objects, characters, figures, or colors used to represent abstract ideas or concepts.
The jabbering bird symbolizes the lack of anything intelligent to say about war. Birdsong rings out alone in the silence after a massacre, and “Poo-tee-weet?” seems about as appropriate a thing to say as any, since no words can really describe the horror of the Dresden firebombing. The bird sings outside of Billy’s hospital window and again in the last line of the book, asking a question for which we have no answer, just as we have no answer for how such an atrocity as the firebombing could happen.
On various occasions in Slaughterhouse-Five, Billy’s bare feet are described as being blue and ivory, as when Billy writes a letter in his basement in the cold and when he waits for the flying saucer to kidnap him. These cold, corpselike hues suggest the fragility of the thin membrane between life and death, between worldly and otherworldly experience.