Do They Really Need Your Help?

Nestling Finches, 7 days old - both parents will be seen frequently

Many people watching a nest of baby birds often believe that the nest has been abandoned because the mother bird has not been seen. The parents take turns to sit on the nest and keep the babies warm usually only in the first couple of weeks. As the babies get bigger, both parents are seen less often as they gather larger amounts of food. At this point the nest is very full and the parents only visit their young for a split second to feed them. The babies by now have begun to lose their fuzz and grow feathers, making them able to thermoregulate. 

Same finches, 14 days old - pre-fledging

Only if the parent has been killed, the babies are truly orphaned and may need your help.

The best way to tell if a nest is being cared for by its parents is to monitor the poop. Look for fresh, moist  droppings at 20 minute intervals.
If the babies are pooping, someone is feeding them! Leave them alone!

A nestling baby that is found on the ground should be placed back in the nest if it is not injured. If you can not locate the nest or the baby has an obvious injury, it needs to be brought to a licensed rehabilitator for care. Place it in a shoe box with a towel inside. Do not offer the baby anything to eat or drink - you may aspirate it! Provide an additional source of heat as the baby can not keep itself warm. The shoe box can be placed on a heating pad set at LOW or sock filled with dried rice heated in the microwave for 1 minute or until hot. Place underneath a towel and next to the babies. If none of this is possible, hold the baby in your hand until you get it to a rehabilitator.
In the rare event you have to overnight the baby, you can offer it some soaked dog or cat kibble. Soak the kibble until it is moist like a sponge and only if the baby freely opens its mouth, pop small pieces inside. Never force feed! This will keep a nestling alive until the next morning but should only be done when you have no other choice. A rehabilitator will know the proper diet necessary for each specie of bird that consists of many different ingredients. Never try to raise a song bird by your self. You will be breaking the law and it will most likely end up dying.

Myth Buster: Parents will NOT reject their young after being handled by a human. However, they will abandon a nest that is constantly being disturbed by people.

Reconstructing fallen nests

High winds may bring a nest to the ground. If possible place the whole nest snugly inside a similar size basket and secure close to the original location. If the nest is found in pieces construct your own out of an appropriate size basket lined with soft material. Create a concave shape to keep the babies close together. 
Mud nests that were attached to a stucco wall in a high eve can be reconstructed and fixed to a ladder or pole that leans underneath the original location. Be sure to provide some camouflage from predatory birds by placing foliage across the top of the basket.

This hatchling needs an additional source of heat as the short growth of pin feathers does not provide sufficient warmth.

If you have to chase it, it doesn't need to be rescued!

Keep your cats indoors during baby bird season in spring and summer or limit the hours that they are outside to the hottest part of the day. They will be more likely to find a shady spot and sleep instead of hunting. A special collar called the Liberator Cat Collar can be purchased online. This has been proven to be 80 % effective. Wandering cats entering your yard where there are songbirds, can be squirted with a hose. They hate it but it won't harm them. 2.7 billion songbirds are killed by cats each year.

The same rules apply to humming birds as they do to other song birds. The parents do not abandon the nests and they spend several weeks on and off the ground while learning how to fly. Meanwhile their parents are off finding food. Do the poop test by checking  for little black dots that are several feet away from the nest. Fledglings should be picked up off the ground and placed in a nearby tree if they are in danger.