If pet birds are not given a proper diet, they can suffer from nutritional disorders. One such nutritional disorder is iodine deficiency, which is common in budgerigars.
Iodine deficiency affects a bird's thyroid gland -- enlarging it from its usual size of three millimeters, to about about one centimeter, or more. (The swelling of thyroid gland, due to iodine deficiency, is called Goiter.) For birds, the thyroid gland is located in the neck and is one of the glands that maintain proper function for various bodily organs.
Birds deficient in iodine will have a lump on its neck; this is due to the enlarged thyroid gland. The animal will also have difficulty breathing, usually recognized as loud and harsh breaths, wheezing, and clicking. Some birds will have difficulty eating or regurgitate food, while others will less tolerant to stress and express behavioral problem.
A gland found in the neck of humans and animals that secretes glands responsible for metabolic rate, calcitonin, and others.
Returning food that has been swallowed into the mouth; often results in vomiting
An enlargement of the thyroid due to an iodine deficiency