If the mother sees you in the yard she will not come near. In addition, if a bird is injured, it needs help and cannot be placed back in the nest. Birds that are cat caught are assumed to be injured although they may not appear to be. If a bird is featherless, it needs heat. If baby doves are found on the ground, it is usually difficult to find the nest to put them back.
Doves make very poor nests which get blown down easily.
Pigeons usually don't make nests. Juvenile pigeons are fully feathered and very docile, and rely on their parents for a long time. If you're not sure the bird needs attention, call a rehabilitator. If an adult bird can be caught, probably something is wrong and it needs help. Birds and rabies Rabies has been produced in birds experimentally, however, it has never been found in wild bird populations.