If baby birds are clearly injured or in imminent danger, contact a licensed wildlife rehabilitator. But if featherless or nearly featherless baby birds have fallen from their nest appear unharmed, put them back in the nest if you can do so without danger to yourself. (It’s a myth that birds will abandon their young if a person touches them.)
Fully feathered birds:
If the original nest was destroyed or is too high to reach, hang or wire a small, shallow wicker basket close to where the original nest was. Woven stick baskets from garden stores or supermarket floral departments work well; they resemble natural nests and allow rain to pass through so the birds won’t drown. A plastic bowl-shaped container with holes punched in the bottom for drainage will also work. Line the nest with soft grass, taking care to avoid anything that the babies might get entangled in. Learn more about building a surrogate nest for birds. Adult birds won’t jump into anything they cannot see out of, so make sure the basket is not too deep. Put the fallen babies into the new nest and keep watch from a distance for an hour to make sure the parent birds return to the new nest to feed their chicks. Watch closely, because parent birds can be quite secretive. If they definitely do not return, contact a licensed wildlife rehabilitator.
Birds with fully feathered bodies but short or non-existent tail feathers may be fledglings (adolescent birds who have left the nest). You might see them hopping on the ground, unable to fly. This is normal; birds learn to fly from the ground up! Fledglings might remain on the ground for a few days or even a week, supervised and fed by their parents a few times each hour before they get the hang of flying. You can tell if the fledglings are being fed by watching from a distance to see whether a parent bird flies over to them, usually a few times an hour. You can also look for white-grey feces near the fledgling. Birds defecate after being fed, so the presence of fecal material means that the birds are being cared for. Be sure to keep cats indoors and dogs leashed until the fledglings are old enough to fly. If you are positive that the parents aren’t returning to feed the babies, you should contact a licensed wildlife rehabilitator.