They not only work together, but too much or too little of one of them can affect the body's ability to use the others. Thus a bird given a diet rich in calcium can show signs of calcium deficiency if the phosphorus or Vitamin D3 levels are not in proper balance. Calcium is used for bone formation, egg shell production and blood clotting. It also affects the heart, muscles and nerves, as well as some of the body's enzyme systems. Calcium can also be found in body fluids.
Skeletal calcium is comprised mainly of calcium phosphate with some calcium carbonate.
Calcium carbonate is the main compound found in egg shells. Higher amounts are required for breeding and growth. Although some birds on all-seed diets can experience hypocalcemic seizures, these seizures are rare except in African Greys. Care must be taken with vitamin supplements not to provide too much calcium. Cockatiels, budgerigars, some grass parakeets and finches live in arid climates and eat mainly lower nutrient, seed diets.