Wild rabbits are different from domestic ones. Wild baby rabbits probably do not need your help. If you find a nest do not touch or move them. Unlike other species the mother bunny feeds her babies only twice a day, usually at dawn and again at dusk. At other times she is away from the nest in hopes of keeping the attention of predators away from her babies.
If you are not convinced that the mother is alive you may gently separate the tall grasses concealing the nest and check the coloring and temperature of the babies. If they are pink and warm, they are fine and are being fed. If the babies are blue or gray and cold they are in serious trouble and mom is probably no longer alive. These babies should go to a wildlife rehabilitator or a rabbit specialist vet without delay. Know in advance that it is very difficult to successfully nurse wild baby rabbits back to health, even by experienced individuals.
To check for mom visiting the nest when you are not around, you can gently put a few strands of wild grass or straw in the grass just above the babies in the nest. The trick is to create a particular pattern with those grasses, maybe something as simple as a star or an “X.” When you return to visit the nest some twelve hours later, if your pattern has been jumbled or is gone you will know that the mom has been returned to care of her youngsters. An undisturbed pattern indicates that the mom has not returned and the babies’ coloring and temperature as described above should be checked.
Please note that it is a myth that a mother will not return to her babies if she smells human scent on them or if the nest has been disturbed. If you have taken wild baby rabbits out of their nest because you thought they were orphaned but now are not sure, return them right away! If the original nest has been destroyed you can make a new one with soft towels a few yards away.