During the late spring and early summer, it's not uncommon to find "abandoned" baby birds. People often worry that the baby won't be taken care of by the parents and take the baby into their home instead. If you attempt to "rescue" a wild baby bird, your biggest concern may be how much and how often to feed it worms. The answer depends on the species and age of the bird you find.
Not all birds eat worms, as adults or babies. Some species feed their young seeds, fruits, other insects, nectar, or vegetation. Others feed their babies regurgitated food (also called "crop milk). Very few feed earthworms to their young, so it's imperative to first identify what kind of bird you have. Robins and starlings are examples of birds that can eat worms.
Your first step should be to call your local bird rescue or rehabilitation center. They can help you figure out if the bird you found actually needs help and they can tell you what to do until they are able to take the bird.
Get help identifying the bird's species, determining whether it needs help and confirming that babies of that species eat worms.
Be prepared to feed the baby three to four mouthfuls every 30 to 60 minutes during the day. The older the baby, the less often you'll need to feed it. However, the baby's diet should not be solely worms. Robins are also fed other insects by their parents, for instance.
It is illegal to keep almost any species of wild bird in your home unless you have a permit from the U.S. Fish and Wildlife Service. Without proper training, it's more likely that you will kill, torture, or injure a bird in your attempt to help. Now that you've started nourishing the baby, get it to a bird rescue center as soon as possible.
Most "abandoned" baby birds are not really abandoned. It's normal for babies that are learning to fly to wind up fluttering about on the ground. The parents are usually nearby, but they won't return to feed their baby until things appear safe. Letting the parents take care of the young is the best answer. It's extremely difficult to keep a wild baby bird alive in captivity. Leave the baby alone unless it's in the middle of the street or otherwise in harm's way.