Living World Iodine Blocks Calcium and iodine deficiencies are common in many caged birds because these vital nutrients are lacking in standard diets. Living World® Iodine Block contains essential minerals missing in seed diets and helps prevent mineral deficiencies. Fortified with calcium and phosphorous, Iodine Block is complementary pet food that is beneficial for all caged birds. Iodine Block helps in the prevention of brittle bones (lack of calcium), enlarged thyroid in budgies (iodine deficiency), egg-binding (lack of calcium), and tremors. Size: Small