It is very important that changes to the diet of your bird should not be made abruptly. In other words, it's best to alternate between different types of food and offer your bird a range to choose from. For example, each time you offer seeds to your pet, you can also include a small piece of fruit or vegetable on the side to see which one they prefer. It is natural that your bird doesn't eat all variations of bird feed sold or every piece of fruit that your offer.
Your bird may not even like the common bird feed that is sold in supermarkets or pet store. If this is the case, the transition to another form of food can be made as described in the paragraph above. However, if your bird is not convinced by conventional bird food that is sold in packets, there are always natural alternatives that will keep your bird well nourished, such as raw seeds, fruit and vegetables.