Dry seed is high in fat (one sunflower seed is equivalent to a human eating a deep fried Mars bar) and very low in protein and essential vitamins and minerals.  This causes lots of problems including poor feather quality, obesity, fatty lump formation, complications associated with excess fat in the liver, weak bones, respiratory disease, reproductive problems, and more. 
Seeds, breads, toast, dried fruits and nuts, and plain crackers should be reserved for use as treats, which can be used in small portions for training. 

 
Converting from a seed diet should be done under the direction of your veterinarian.