Many birds in the wild have evolved to fill particular niches, so you can expect many species to have quite specific dietary requirements. For many species, a diet of seeds is just fine. Some species will require fruit and nuts to get all the nutrients they need. Others will require insects and meat to fulfill their requirements. It is always important that you check first to be sure of just what dietary requirements your particular species of bird has in order to feed them properly.
Bird food often comes loose, but it can also come in sticks or still on the stalk, which is often the case with millet. This gives your pet an extra challenge when it comes to feeding time, and helps to simulate conditions that they would encounter in the wild. Providing such a challenge helps to relieve boredom for them.
If you have selected the right type of food for your bird then in most cases it would sufficient for them. Sometimes though, it might be necessary to find a food that is supplemented with vitamins and minerals for maximum health such as pellets or crumble.