I was contacted last week by someone who was asking what to do, as they had found an injured bird...and this is a hard one to answer, as I'm sure some people will be upset. In the end, and in this particular case it had a happy ending. This particular bird was injured, and it was taken in and put in a container. I advised to give it water and some feed, then to cover the container - and see if it recovered, as many birds are hurt when they collide with something (like windows). The next day, i am happy to report the bird flew off when the container was opened. However, if it had not recovered, then my advice was firstly to determine if it was a rare bird (like an owl, or crested serpent eagle), and if it was indeed rare, then contact SPCA or Kadoorie or AFCD, and they would determine its treatment. If it was a common bird (pigeon, crested Mynah), then my advice is to place it back in the wild and let nature take its course. The other options would take a lot of time and energy that could be spent elsewhere - and would probably end in the bird being euthanised anyway. Or you can take it to the vet, and then pay for its treatment - which is essentially what you asking the other services to do, and they are simply too busy to care for each and every animal that comes their way, so like in war-time, they have to operate a "triage" system. And they do it very, very well, with a rigorous and effective line of decisions and communications regarding species and treatments.
Anyway, here is some advice from those institutions about what to do if you find a baby bird.