Birds
In birds pituitary gland secretes hormone prolactin. Prolactin stimulates production of “Pigeon’s milk” in pigeon’s crop. Prolactin also stimulates and regulates broodiness and certain other kinds of parental behaviour and along with estrogen stimulates full development of the brood pouch. Brood pouch helps to keep the eggs at temperature between 33 and 37°C. Birds thyroid gland produces hormone thyroxine. It regulates normal development of feathers and the molt cycle and plays a role in the onset of migratory behavior. In male birds the teats produce hormone testosterone. It controls the secondary sexual characters of male such as bright plumage color, comb and spurs all of which strongly influence sexual behaviour. Below parathyroid glands are ultimobranchial glands which are small paired. They secrete hormone calcitonin involved in regulating blood calcium concentration. Bursa fabricuis is a sac that lies just dorsal to cloaca. Its tissues produce secretions that are responsible for the maturation of white blood cells which play important role in immunological reactions.