The maximum amount of formula to feed to any baby prior to weaning is about 10 percent of his body weight. The length of time between feedings is determined by the amount of time it takes his crop to empty, usually 4 to 6 hours. As the baby grows, use more formula and fewer feedings. As the baby matures, he will begin to resist feeding. When feedings have reached only two or three a day, start your bird on solid food in the form of softened pellets or table food.
For more information, please read the story How to Feed a Baby Bird