I am no bird expert, but as a child following a bad wind storm I did care for several that fell from their nests, one that was abandoned by its mother.
I fed them room temperature milk from a eye dropper. Though they do not normally eat such a thing it worked and they liked it. A little bit of water but not enough so they can drown in it may be quite helpful to my opinion.
If grown..... birds generally eat nuts and seeds. I fed one starving in a snow storm once, and fed it nuts and such, I had in a granola type cereal. It worked just fine.
"This order considers that progress can be achieved more rapidly during a single month of self-transformation through terrifying conditions in rough terrain and in "the abode of harmful forces" than through meditating for a period of three years in towns and monasteries"....Takpo Tashi Namgyal.