A varied diet is extremely important to a pet bird. A bird has no control over the foods that you offer him, and if you only offer seed, his diet will be seriously deficient in very important nutrients. He won’t be strong, energetic, and have the beautiful appearance that only really healthy birds have. He will be unable to put up much resistance to illness or disease and his life will be shortened considerably.
A seed-based diet is NOT what birds exist on in the wild. It is not known what all their diet consists of, but sunflower seeds and peanuts (among many others) do not even exist in the wild where most species exist naturally. Some human, somewhere, arbitrarily decided that parrots should eat seeds, and since then, it’s become accepted as truth, even by many birds, to their own detriment. Many seeds are like candy to birds – there is not much to them nutritionally; they are full of fat and empty of most of the vitamins and minerals that birds need to be healthy.
There are some seed mixes that contain less seed and more pellets and dried fruit and vegetables. This is what I use as the food that is always available in their food bowls. I also offer all of my birds, every day, some sort of fresh food. I vary what I give them, and alternate. They seem to love the surprise element – what’s going to show up in my bowl today?
A pelleted diet is good for a parrot, assuming that your bird will accept an all-pellet diet. (With occasional treats) Finches and Canaries naturally eat seeds, but need fresh food and also some live food also. Lories, Toucans, and other birds need special diets which include nectar and specialized levels of nutrients.
I believe, with a good pellet-seed-dried fruit mix and daily offerings of fresh fruit, vegetables, cooked pastas and grains (like rice and beans) as a base, my birds get a good diet. I don’t routinely offer a vitamin supplement, since I provide them daily with a balanced menu. I do try to offer them foods that are good sources of Vitamin A, since that is a common deficiency in pet birds.
Human foods that are really bad for birds are chocolate, rhubarb, alcohol, caffeine and avocado, and these are not just bad for them; they are POISON. You should be very careful to never let any of your birds have anything with those things in it.