Sick birds will often eat strange things in strange amounts. They may overeat the grit and compound the problem. If the bird is staying on the bottom of the cage then place the seed and water within easy reach. If the bird is not perching this may require putting seed on the floor of the cage and the water in a shallow dish. Provide 12 hours of light and the same amount of darkness.
Sick birds require much time to sleep yet the light is necessary to encourage eating.
Ill birds require added nutrition and vitamins yet they often will not eat readily. Offer any of the bird's favorite foods. Offer peanut butter in a small dish. Sparrows, mocking birds, black birds, blue jays, hawks, owls, doves and pigeons. As this partial list illustrates Altricial baby birds are commonly encountered in this area, most commonly in the Spring of the year when most birds are nesting.