My parakeets are picky eaters

When I got my parakeets I first read a book invading for them so I woukd know what to do. The book and the pet shop own recommended giving them pieces of fruits and vegetables. I've tried this but neither of them have ever given it a try. I don't know why, but it's like they are convinced that only sees and millet is food and these other things are just foreign objects invading their cage.

It is not good to feed them only a single type of seeds.
You need some fixed seeds. For example, I feed my budgies millet, oats, canary seeds, along with some veggie seeds.

Even with mixed seeds, it is not enough. The birds need more vitamins in their diet.

You need to feed them leafing veggies. Mine love it, and basically they go crazy when I feed them leafy veggies. My birds also liked broccoli for a while before somehow they got bored with it.
Do not feed them fruit, as there is too much sugar in them. Some fruit seeds are toxic to the birds.

We can never duplicate their true natural diet since they would chew on varies plants and seeds every day in the wild, but we can at least try to provide a well balanced diet that is as close as to their natural diet as possible.
There is also the need for mineral supplement. If you check my budgie threads, you'd see the mineral rock in the cage. It contains varies minerals the birds need.