My house duck who usually LOVES peaches and apples, the past two days has only taken a bite or two and then wants nothing more to do with them. This is the same duck who would eat a whole (chopped up) peach for breakfast and want more when he was done. Should I be worried that he is no longer interested in his favorite foods, or is it normal for ducks to get bored with a food? I just don't want to be missing a subtle sign of illness. He's already on antibiotics for sneezing, so I am nervous that perhaps this is a symptom of something more serious (and perhaps the sneezing is not just a mild URI afterall). Opinions?