Try not to disturb the rabbit when it is under the deck. This will help it conserve its energy. Other than that, you don't need to do anything. The rabbit will find the food that it needs. And your deck apparently provides protection against the weather that the rabbit finds suitable. During the winter, rabbits will often eat bark or small twigs off of shrubs. So if you have bushes in your landscaping, you may notice that the rabbit has nibbled on them.
