270 RAYMOND PEARL 



a record is obtained of every egg laid and of the hen which laid 

 it. It is further the practice to confine birds which are broody 

 in small coops until the particular manifestation of the instinct 

 shall have disappeared. Beginning in December, 1907, and 

 continuing until the present time, the practice has been followed 

 of making a record of the date on which any bird is put into 

 confinement for broodiness, and also of the date on which she 

 is released from confinement as "cured." These records were 

 made by putting ' B " in the space corresponding to the date 

 of onset of broodiness and " O " in the space corresponding to 

 the date of release, on the poultry house egg record sheets. 

 Records so obtained form the material of this paper. The records 

 here discussed came, in the main, from 850 Barred Plymouth 

 Rock pullets hatched in the spring of 1907. This breed will 

 alone be considered in this paper. 



In a critical consideration of these data the question at once 

 arises as to their accuracy. Does the instinct of brooding 

 manifest itself with such clearness that the recorded date of 

 onset corresponds Substantially with the actual ? And further, 

 to what extent does the date of release measure the actual 

 subsidence of the instinct ? These questions may be considered 

 in order. The onset of a period of broodiness is, at a certain 

 stage, marked by a characteristic behavior which is immediately 

 and certainly recognizable by an experienced poult ryman. 

 Whether the stage at which this characteristic behavior begins 

 marks the absolute beginning of the physiological state which 

 underlies the instinct of broodiness is a question impossible of 

 answer and really of no particular significance from the present 

 standpoint. This behavior is the objective criterion of broodiness. 

 Whatever preliminary internal or subjective stages the bird 

 may go through leading up to this objective behavior constitutes 

 a field of inquiry separate from the study of the behavior itself. 

 This leads to the question as to whether the behavior connected 

 with the onset of broodiness is so characteristic as to be easily 

 and certainly recognizable. Of this there can be no doubt. 

 The following characteristics are perfectly definite and obvious. 



1. Continued sitting on the nest. As soon as she is thrown 

 off the nest, the " broody," in the early stages, promptly returns. 



2. A peculiar " clucking " note, not made by the bird at any 

 other time in her life. 



