How can this bird survive?

Today I find a baby bird (I think it's a White-Throated Sparrow) at the corner of a subway staircase, waiting to me an intentional or accidental end. It was away from it's family and I saw it face close encounters with death as careless people nearly stomped it out. My mother rescued it and brought it home. It won't learn to fly or scavenge for food with us as owners. What can I do to return it to it's path in life as a New York City street bird.