Found a baby bird, what to feed it? Urgent help needed!

What an interesting post this has all been! I've had pet birds for the past twenty-some years, but I wouldn't know what to tell you to feed a baby wild bird. I would think those worms you've been giving it are a good food source. You could call the place I get all my parrot food from. They might be able to help you with a meal type food to feed this wild bird. They always have various baby birds at the store, feeding them and caring for them. http://highlandtropicalfishandbird.com/
I hope your little bird grows strong and healthy! I remember working at a store right in the downtown area on main street when a baby bird hopped inside the open door. I put it back outside, hoping it would go back "home," but it hopped back inside the store. I looked all around, but didn't see where it could have come from. I started worrying someone might step on it or it would go out in the street and get run over. The lady who owned the store next door, took the bird home with her. It looked much the same as yours. I don't know what ever happened to that little bird, what she fed it, if it survived...