Imprinting is "A rapid learning process by which a newborn or very young animal establishes a behaviour pattern of recognition and attraction to another animal of its own kind or to a substitute or an object identified as the parent." When rearing a newborn animal, it is very difficult to avoid imprinting as it takes a lot of effort of not letting it hear your voice or not letting it see your hand, for example, feeding it. In the wild it is therefore always preferable to let nature take its course and not to interfere and pick up fledglings that have left the nest and landed on the floor. Normally the parents are close-by and will feed it until it is able to fly. That is how they grow strong and learn to fly.
I know predators are always a worry, but unfortunately that's how nature is. Once you "save" it (we all have that instinct), releasing it back to nature is always difficult as it has not learnt the necessary survival skills to ensure it makes it in the wild, where it will then probably perish anyway. The other alternative is then spending the rest of its life in a cage, definitely not an ideal situation.