Having rescued a few wild baby birds, here is what we did.

While holding the bird, we took a pair of long nose tweezers and took small pieces of bread dipped in warm water and fed the bird the way it's mother would. We also collected insects for it.

Make sure the bread or insect is right at the tip of the tweezers and keep them closed while feeding the bird.

Does it have all it's feathers? Does it attempt to fly? Do you know what kind of bird it is. Would you be able to get it into a bird cage? We did this once with a baby black bird, put it in a bird cage and had it on top of the bar-b-q on the back gallery and the mother bird came down to feed it.

Have you tried feeding the bird by hand to see if it would take the food?

Sorry for all the questions.