Your bird needs to eat most of the berry without wasting too much. Once a bird is eating the berries, then you can work on having her eat more of each berry. Reduce the amount of berries you give her at a time, and do not give her more until she has eaten what she has. In the wild, if food is abundant, then a parrot will eat a few choice bites and discard the rest of the food. This is nature’s way of feeding ground dwelling creatures and replanting the environment. In captivity, we tend to offer too much food at one time, so the bird follows instinct and wastes a lot of food. If she learns there is not an endless supply, she will learn to eat more efficiently. As long as discarded bits have not been soiled with feces, you can pick them up and place them back in her dish.
Thank you for asking Lafeber,