Environmental Endocrinology and the Control of Annual Reproductive Cycles in Passerine Birds

The endocrine glands and the hormones secreted by them are components of a communication system that, among other functions, is involved in adjustment to changes in the external environment. The spectrum of such adjustments in endocrine functions induced by changes in the environment ranges from rather direct adjustments such as those involved in osmoregulation or thermoregulation to those involved in periodic reproductive function. The latter are the subject of this communication.