We had a baby bird fall out of a tree by us. Our local wildlife rehab place said to bring it in as soon as possible because success with handraising is very low. They also said, don't try to replace the bird in the nest - it won't work either. If you have a wildlife rehab - that would be your best bet. They have the incubators and the knowhow for what they eat to ensure that the bird has the best chance for surviving.