This fascinates me. If I assume that the parrot only imitates a sound, berift of meaning, then I think that I would leave "bonjour" as it is in the english translation. And place it in double quotes. Contrairly, if a computer were speaking the sentence, I would translate "bonjour" to "hello". This because the computer is functioning at the level of meaning, whereas the parrot is, I believe, functioning at the level of sounds.