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

I can't be sure, but the most common birds around here are Eurasian Tree Sparrow (Passer montanus). They are everywhere here, on the sidewalks, in the trees, on the buildings.

The bird does not seem to be injured. It can jump fine, and always extend its wings once in a while but can't really fly. It's not yet fully covered by feather. When it turns around the head to clean its own feather I can see its skin around the neck.

It is quite warm here. My room temperature right now is about 79F or 26C. Is it warm enough? I turned off the air conditioning just for the bird.

As for feeding, I tried a little egg yolk with no luck, although the bird was taking the drop of water from my finger.

So I had already rushed to a pet market and brought back some live worms. I forgot to ask what worms they are, but these worms seem to be quite tough skinned.
Here is a picture I took. Do you know what worms these are?



At first I had no luck feeding the bird with the worm whole, I cut off the worm's head and squeeze some stuff out and the bird ate a little. I tried again just a few hours ago, the bird actually swallowed 2 worms whole! Then an hour later, it swallowed another headless worm. The bird had pooped twice in my hand, so I guess its fine for now.

I am not certain if feeding a single type of worm is good enough nutritious for it.

What else can I feed? It's really hard to get the bird just to swallow 3 worms.