Vitamin A --------- Vitamin A must be readily available in the diet and consumed in adequate quantities by caged birds to maintain healthy eyes, skin, feathers, and linings of their gastrointestinal, respiratory and reproductive tracts. Amazon parrots seem to have the most trouble with vitamin A deficiency. Foods rich in vitamin A include cod liver oil, cooked liver, egg yolk, apricots, corn, carrots, squash, sweet potatoes, broccoli, spinach and parsley. Seeds are notoriously deficient in vitamin A.