I'm sorry that your question wasn't answered in a timely manner. We don't have many avian vets on this site. The "poop" you've described is likely due to dehydraton if the urate portion (the "white") is also tubular and dry. In addition, very bulky droppings indicate maldigestion, malabsorption, a coelomic (abdominal) growth, or pelleted diets. An avian vet (please see here: www.aav.org) can perform a thorough physical exam including diagnostics in the form of blood and urine tests in an attempt to clarify if maldigestion (a lack of digestive enzymes produced by the pancreas) or malabsorption (inefficient absorption of digested ingesta from the GI tract) are present.
Nutritional imbalances are a common cause of illness in our pet birds. Do your best to transition him away from seeds. Seeds should compose less than 20% of his diet. A diet of mainly seed and nuts has excessive fat, carbohydrates, and phosphorus; marginal protein; adequate vitamin E, and are deficient in amino acids, calcium, available phosphorus, sodium, manganese, zinc, iron, vitamins A, D3 (necessary for efficient absorption of calcium), K, and B12, riboflavin, pantothenic acid, choline, and available niacin. Ideally, a balanced pelleted diet such as can be found here: www.harrisonsbirdfoods.com or here: www.lafeber.com/pet-birds should be fed as well as hard boiled egg yolk, pancakes and cornbread, the tops of fresh greens, dairy products such as yogurt and cheese, fresh fruits such as apples, pears, melon, kiwi, and berries, vegetables such as broccoli, carrots, beets, asparagus, cabbage, sweet potato, and squash, and even tiny pieces of meat.
Please respond with further questions or concerns if you wish.