STUDIES ON THE PHYSIOLOGY OF REPRODUCTION 

 IN THE DOMESTIC FOWL. VII. DATA REGARD- 

 ING THE BROODING INSTINCT IN ITS 

 RELATION TO EGG PRODUCTION » 



RAYMOND PEARL 



INTRODUCTION 



The extensive poultry plant maintained by the Maine Agri- 

 cultural Experiment Station for experimental purposes offers 

 an exceptional opportunity for the study of the habits, instincts, 

 and behavior in general of the domestic fowl. While hens have 

 been kept under domestication for a very long time, comparatively 

 little systematic study of their adult behavior has ever been 

 made. A splendid field of work is open here for the student of 

 animal behavior. The writer and his associates are collecting 

 data in certain directions within this field. Particular attention 

 is being paid to those features of behavior which have to do 

 with the processes of reproduction. It is the purpose of this paper 

 to present a part of the material which has been collected regard- 

 ing the brooding instinct in the hen. This material in part 

 illustrates some facts which have not, so far as the writer is aware, 

 hitherto been brought specifically to the attention of workers 

 in animal behavior, and in part, it is believed, brings to light 

 some new facts. This paper is in no way to be regarded as an 

 exhaustive treatise of the subject of" broodiness. Certain of 

 the problems involved demand an extensive and detailed statis- 

 tical treatment and our data on these are left for discussion at 

 another time. 



The brooding instinct belongs in the category of what Herrick 

 (3) has well called " cyclical instincts." This author has pointed 

 out that primitively the following cycle of events appears in 

 the reproductive activity of birds: ' (1) Spring migration; 

 (2) courtship and mating (often attended by song); (3) selec- 



1 Papers from the Biological Laboratory of the Maine Agricultural Experiment 

 Station, No. 65. 



266 



