Before addressing the subject of what to do if you find a baby bird, understanding a bit of avian breeding biology might be helpful. Depending on their development at the time of hatching, birds are said to be either altricial or precocial. Altricial young at hatching are helpless, usually naked, have their eyes closed and are totally dependent on the parents for food and care. They are hatched in well-constructed nests built by their parents, usually in trees, bushes or shrubs, and are called nestlings. Robins, crows, cardinals, doves and other songbirds, plus many other species, are altricial birds. Nestlings grow quickly, become feathered and, depending on their species, leave the nest in two to four weeks. When they leave the nest, or in bird terminology, fledge, the young are called fledglings. Most fledglings are still tended and fed by their parents (even on the ground) for a short period of time until they become completely independent.
Precocial birds are much more developed at hatching. They are covered with down feathers, have their eyes open, are able to run about (or swim) soon after hatching, and can feed themselves at an early stage. Precocial chicks are usually hatched in nests on the ground and remain with their parents until self-sufficient. Quail, pheasants, gulls, ducks, geese and shorebirds are a few examples of precocial birds.