Often a wild mammal mother will be off feeding for four or more hours. This is especially true with fawns, whose primary defense in their first couple of weeks is camouflage and lack of scent. Just remember, no matter how hard even the most experienced rehabilitator might try to match the care these animals would receive in the wild, humans are still poor foster parents. Be sure they really need your help before you intervene. They leave the nest to follow their parents within hours of hatching.
Precocial birds learn to forage within three or four days.
They rely on their parents for warmth, guidance, supervision and protection from predators. If separated from their parents, it is not likely that they will survive. Young small altricial birds such as robins, goldfinches and swallows hatch with no feathers and their eyes are closed. These small altricial birds must be able to get around before they can start to learn to forage. It may take small birds as much as 3 weeks to grow strong bones and feathers and become strong enough to leave the nest.