Sulfites

Many dried fruits and vegetables contain sulfites to preserve them. Longer shelf life is what many consumers want. It also makes the fruit look better. However, like some humans, birds can react to these sulfites. Some birds may display bizarre behavior, including plucking and even aggression. Use dried fruits and vegetables from a health food store. These do not include sulfites in their foods.

Reference: "The Healthy Bird Cookbook" by Robin Deutsch