I have rehabbed several types of wild birds, and this is a good basic formula for the young ones that fall out, or get blown out of their nests, or that are orphans. Older wild birds need Game Feed, or Wild Bird Feed when they are old enough, or well enough to eat it. Do not feed them Chicken Feed, as several types of birds can't tolerate some of the ingredients.
1 Can Dog Food
1 Multi Vitamin (dissolved)
4 Tums (most birds like fruit flavored best)
1 Can Green Beans
1 Baked Sweet Potato (cooled and peeled)
Water (enough to make it a bit thinner than baby food)
Mix all in food processor or blender. I would put about 4 tablespoons of this mixture into sandwich bags. Keep one out, and freeze the rest. This will give you at least a weeks supply. To feed, I take a drinking straw, cut in half this gives you two. Pinch one end of the straw and cut in half lengthwise about 3/4 of an inch. Cut off the top portion, and round the corners. Like the straws from the convenience store for frozen drinks. Load the end of the straw with food, and gently pry open the birds mouth, and let mixture slide in. Do this every 3 - 4 hours until it's old enough, or able to eat on its own. Yes, you will probably need to get up during the night for a feeding or two, for a few days until you are sure it is getting enough during the day to sustain it through the night. Offer water, and food for them, but don't stop feeding them until you are sure they can eat on their own. Make sure they are warm enough, and keep them out of drafts. Use a clean rag, or towel for them to snuggle down in at night, if they aren't old enough to roost.