I recently found a baby sparrow, actually my cat did and it didn't even have all of its down or feathers. I put it in a box with a towel covering it and also a heat light, not to warm though. The towel keeps the bird from drying out. I called different animal rescues and didn't get anyone to take it, so I did the next best thing and called a
pet store who specialised in birds and they told me to feed it baby bird food with a dropper. It has all of its wings and down now but it thinks I'm its mom now, so I went and got a cage and a female finch and put it in with her and now she is the mother, sort of (I still have to feed it with a dropper). good luck.