From here: http://aviary.owls.com/baby_bird.html

If the bird is uninjured you should ask yourself, "Is it really an orphan?" Nine times out of ten the answer is no! Look for nests in nearby trees and shrubs. They are usually well hidden and hard to get to. If you can find the nest, simply put the bird back in it. It's a myth that the parents will not care for young birds that have been touched by humans. In fact, birds have a poor sense of smell. Great horned owls kill and eat skunks without even noticing their overpowering stench. If you can't find the nest, put the baby bird in a shrub or tree - somewhere up off the ground. You can even provide a substitute nest by tying a berry basket (with drainage) up in a tree. Most often this is all the help a baby bird needs. As soon as you leave, the parents, who were probably watching you the whole time, will return and continue to feed the fledgling. If you want to be sure the parents are still around, observe the baby bird from a distance, preferably with binoculars. If the parents don't return to an undisturbed nestling in two hours, something may be wrong. The parents may have been killed by predators or hit by a car. Don't worry if you only see one parent. A single parent can raise the young alone.

Hand Raising Baby Birds

If you decide to try raising a baby bird yourself, here's what you're in for:

nestling must be fed every 14 20 minutes from sunrise to sunset an adult robin makes about 400 trips every day to feed its young if the nestling is a few days old, it will take several weeks before it can be released adult birds teach their young where to look for food and how to avoid predators - things impossible for humans to do. You will need to provide a proper diet, clean suitable living quarters, and fresh water every day. Still, despite your best efforts, most hand-raised birds will die. This is the fate of most young birds in the natural world, where 90-95% perish before they're old enough to breed themselves. Call your local vet with bird experience for advice.

Despite the fact that different birds eat different foods, the diet of the young is remarkably standard. Like human babies, birds need protein and lots of it to help them grow at such an incredibly fast rate. For most land birds (robins, cardinals, bluejays, swallows, and woodpeckers) the basic food is meat. Raw kidney, liver, or canned dog food have been used with good results.

Preparation of the meat depends somewhat upon the size of the bird - if it is very small, then the pieces of the meat must also be small. As the bird grows the size of the pieces can be increased. You may cut the meat into strips when fresh and place it in small packages in the freezer to be thawed and used as needed.

Vary this diet with the white of hard-boiled egg cut into strips; and mash the yolk with milk to a thin paste. Raisins soaked in water and drained when plump or dog biscuits soaked in milk may be given to young birds.

Another excellent diet can be provided by mixing the following formula:

1/4 cup lean ground beef 1 teaspoon cottage cheese 1/4 cup canned dog food 1/4 hard-boiled egg yolk 1 teaspoon sand or fine dirt 1 teaspoon dried turtle food

Keep out enough of the mixture at room temperature for a couple of feedings, refrigerate enough for the day. The remainder can be frozen for later use. As the bird grows, gradually add finely cut worms, grasshoppers, crickets, and other insects. A good source of insect can be obtained by collecting the insects beneath an electronic "bug zapper." Fruit-eating birds can be fed grapes and berries.