Wild rabbit babies should be fed specialized formula obtained from a vet, while weaned wild rabbits generally eat whatever vegetation is available in their habitat. It's important to make sure that a mother rabbit has truly abandoned a nest of babies before an attempt is made to nurse the kits since she may be out foraging and only away from the nest temporarily.
According to PETA, rabbits will eat everything from flowers and clover to grass, weeds and vegetables during warm months. In winter months, rabbits turn to any remaining green plants, conifer needles, bark and twigs. Generally, wild rabbits longer than five inches in length don't need to be fed at all, since nature has made them capable of finding food and feeding themselves.