THE BROODING INSTINCT IN THE DOMESTIC FOWL 269 



1 . During the winter months a number of eggs are laid. This 

 constitutes what may be considered a first clutch. 



2. Sometime in the early spring the hen stops laying and be- 

 comes broody. If she is not allowed to incubate eggs the broodi- 

 ness disappears after a varying length of time depending on 

 circumstances. 



3. She lays another clutch of eggs, and 



4. Becomes broody again, and so on. 



This sequence of events — a period of laying followed by a 

 period of brooding — may be repeated several times over. Usually 

 after early summer the tendency to broodiness becomes greatly 

 diminished or disappears altogether. 



It will be seen that this series of events is very similar to a 

 repeated cyclical instinct in wild birds. The normal sequence 

 is broken into at the brooding stage by the fact that the hen is 

 not allowed to incubate. She then begins anew at the next 

 preceding phase of the cycle, viz., egg-laying. Now while this 

 sequence of events is undoubtedly to be regarded as the normal 

 one for so-called " broody ' breeds of domestic poultry, there 

 are numberless variations from it in individual cases. In this 

 paper some of these variations will be described and discussed. 



It should be noted that the behavior ordinarily classed by the 

 poultryman inclusively as ' ' broodiness ' ' really belongs in two 

 rather distinct categories. In the first place there is (a) the in- 

 stinct to sit upon and incubate eggs. This is in many respects 

 an altogether different thing than (b) the instinct to " brood " 

 a flock of little chicks after they are hatched. The two forms of 

 behavior are of course closely related to one another, and object- 

 ively have a number of features in common. But there are also 

 marked differences. It is important to emphasize at this point 

 that the present paper has to do entirely with the first of these 

 instincts, namely that of incubation. In accordance with general 

 usage, I have employed the terms "broodiness," 'broody," etc., 

 to designate this instinct. I desire, however, to make perfectly 

 clear the restricted sense in which the terms are here used. 



THE NATURE AND METHOD OF COLLECTION OF THE DATA 



In the poultry work of this Station the only sort of nests pro- 

 vided for the laying birds are trap nests. Consequently, with 

 the exception of an occasional egg laid on the floor (Cf. Pearl [5] ) , 



