Baby birds generally eat whatever their parents are having for dinner because the parent must regurgitate its food into the mouths of its offspring. Birds, when they are born, are not capable of breaking down food so their parents must first partially digest food to make is safe for baby birds.
Because baby birds rely on their parents for not only food but also for guidance on how to be a bird, it is not safe for a baby bird to be without its parents. Therefore, if you find a baby bird try to restore it to its nest rather than caring for it yourself. If you cannot return the bird to its parents contact a rehabilitation center that can properly care for the young bird.
Different birds eat different things. In the wild, baby birds eat what their parents eat: worms, insects, seeds and so on. However, baby birds can eat different types of food if being cared for by someone other than their parents. Puppy food soaked in water until spongy works well. Finely chopped fruits and vegetables (such as corn or peas) can be used as well as small insects. Wet dog or cat food can be used in a jam if at room temperature.
Baby birds should not be given water to drink. Giving it water could suffocate it. Milk and bread are also dangerous for baby birds.
In addition to providing food for a baby bird it should be kept warm. By placing it on a towel over a heating pad, the bird can stay warm. Just make sure the heating pad is on its lowest setting.
Wild birds cannot be kept legally. If you find an abandoned baby bird, keep it warm and locate a nearby rehabilitation center.