Excessive levels of phosphorous or a lack of vitamin D 3 can make this worse by reducing the availability of calcium from the intestine, but also the amount that can be used from the blood. The result of this dietary imbalance leads to a number of clinical conditions. Birds may become weak, drink excessively, vomit or refuse to eat. Breeding females may have further complications when egg laying. These birds may lay fewer eggs or eggs which are 'soft shelled'.
Fragile bones are another long-term complication.
If left untreated these birds will die. An egg bound bird is an emergency. African grey parrots are particularly prone to calcium deficiency. In this species the main presenting sign is fitting. Most birds are two to five years of age when these fits start.