18 



ENDOCRINOLOGY OF REPRODUCTION 

 IN BIRDS 



Art van Tienhoven, Ph.D. 



ASSOCIATE PROFESSOR OF AVIAN PHYSIOLOGY, DEPARTMENT OF 



POULTRY HUSBANDRY, NEW YORK STATE COLLEGE OF AGRICULTURE, 



CORNELL UNIVERSITY, ITHACA, NEW YORK 



I. Introduction 1088 



II. The Male 1088 



A. The Testis 1088 



1 . Anatomy 1088 



2. The interstitium and its secre- 



tions 1089 



3. Seminiferous tubules 1092 



4. Vasa deferentia 1095 



B. Endocrine Reguhition of Testicu- 



lar Activity 1097 



1. The pituitary ghmd 1097 



2. The pineal body 1103 



3. The adrenal gland 1103 



4. The thyroid gland 1104 



5. Progesterone 1105 



6. Estrogen 1106 



7. Nutrition 1107 



8. Drugs 1108 



C. Fertilization and Sperm Physiology. 1109 



1. In vivo ". 1109 



2. In vitro 1110 



III. The Female 1111 



A. The Gonads 1111 



1. The right (rudimentary) gonad. . 1111 



2. The ovary 1114 



3. Function of the ovary 1115 



4. The oviduct '. 1122 



B. p]ndocrine Regulation of Ovarian 



Activity 1126 



1. Anterior pituitary 1126 



2. Estrogen ." 1130 



3. Androgen 1131 



4. Progesterone 1131 



5. Corticosteroids 1133 



6. Epinephrine 1133 



7. Thyroid hormone 1133 



8. Nutrition 1134 



C. Regulation of Breeding Cycles of 



Seasonally Reproducing Birds. . . 1134 



1. Hypothalamic-pi^uitary system. 1134 



2. Light " 1137 



3. Temperature 1141 



4. Rainfall 1142 



5. Food 1142 



6. Vocalizations 1142 



7. Nesting site 1142 



8. Psychic factors 1143 



D. Regulation of the Reproductive 



Cycle of the Fowl 1145 



1. Use of birds in bioassays 1152 



IV. References 1154 



I. Introduction 



The fascination of avian reproduction 

 with the accompanying migration over 

 great distances, the majestic flight of a 

 flock of geese, the reproduction of penguins 

 at low temperatures in uninhabitable wastes 

 of the antarctic, all these justify a con- 

 sideration of the endocrinology of avian re- 

 production. So little is known, however, 

 about the factors controlling the migrations 

 and of the maturation of the gonads of 

 wild birds. Most of the author's experience 

 has been gained by the study of the chicken, 

 which by selection has become almost a 

 zoologic monstrosity, but nevertheless has 

 been a useful experimental animal. In writ- 

 ing this chapter, the author has tried to con- 

 sider the literature on the subject of avian- 

 sexual-endocrinology both for domestic and 

 nondomestic birds. His aim has been to give 

 both their fair due. The absence of con- 

 siderations of the behavioral aspects of re- 

 production has been deliberate in view of 

 the chapters in this book devoted to that 

 subject. 



II. The Male 



A. THE TESTIS 



1. Anatomy 



^ Aristotle made the observation that the 

 avian testis has a remarkable capacity for 



1088 



