We have put the bird back in it's nest. We think. There are three nests up there (above the entrance to our building) and we picked the one that had another baby bird in it. While this was happening, the mama or daddy bird watched us and then immediately flew into the nest once we vacated.
Hopefully, this was the right nest and the poor little guy doesn't get vacated.
BTW, we read online that if you find a baby "nestling" bird (no feathers) the best thing to do is to put it back in the nest if possible. Second best would be to make a new nest out of a margarine tub or bastket, put some grass in it and hang it in a tree as close to the nest as possible. And contrary to popular myth, a mama bird will not abandon a baby bird if you touch it. Phew...I feel much better. We did everything we possibly could for this bird. The rest is up to Mother Nature.