Found this about feeding PILEATED AND RED-HEADED WOODPECKERS;
Age of these nestlings, all of which were obtained 26 to 28 days after hatching, was determined by inspecting the nests and noting the date of hatching. During the first week after capture, the young were fed a watered mixture of high-protein (34 percent) baby cereal and strained beef every 2 hours during daylight. Nestlings rarely opened their beaks voluntarily for food. They were fed by forcibly inserting the tip of a medicine dropper down their throats and ejecting the watered mixture. Three droppers full, a total of approximately 3 g, constituted one feeding at the beginning.
Quantity of food given and time between feedings were increased progressively for 30 days, until about 8 g were being given three times a day. Each bird was fed until food backed up to the pharynx. Force feeding was discontinued after about 1 month, when all the birds had begun eating meal worms. Some began eating worms within 2 or 3 weeks, but force feeding was continued as a precaution against starvation. Water was always available, but the birds seldom drank. Since the food mixture was moist, it was believed unnecessary to force the birds to take additional water.
It went on to say they fed adults Meal Worms.
http://elibrary.unm.edu/sora/JFO/v03...0313-p0316.pdf