They rely on sensory input from their eyes possibly more than any other species. And light has a tremendous influence on their growth, metabolism, reproduction, and behavior as well. Young quakers, by their very age, are at the most important stage of their growth and development cycle. Nutrition at this point is essential. And one of the most critically important minerals to a bird's overall health and development is calcium.
Calcium promotes strong bones as well as the maintenance of many physiological functions.
Without calcium, birds can suffer spontaneous fractures, which may cripple them for life. Unfortunately, calcium cannot be absorbed by the intestines, nor can its level be regulated, without the presence of Vitamin D3. The process of synthesis requires ultraviolet radiation of a specific wavelength. The most common source of this radiation is, of course, sunlight. Egg production can be increased by artificially creating longer periods of light, simulating natural seasonal light cycles.