BROODINESS IN DOMESTIC FOWL. 101 



Figures 1, 2 and 4 are examples of variability in number of broody 

 cycles. It will be observed that there is a period of production of variable 

 length before the first broody period makes its appearance. This may 

 come soon after production begins (Fig. 1), or may be delayed till near 

 the end of the season (Fig. 4), or even till subsequent seasons. After the 

 first broody period subsequent periods occur in fairly regular sequence, 

 the cycle of broody, rest and production being repeated over and over. 

 It is obvious, then, that the number of broody periods occurring during 

 the first year will be determined in part by the time of year the first 

 brood}^ period occurs. After one broody period it becomes a question of 

 the number of additional cycles that are added before a bird stops laying 

 for the season. In the extreme case of Fig. 4, production was not resumed 

 after the first broody period, which came late in the season. 



In later years there has been much less regularity in the recurrence of 

 the broody periods in that part of the flock bred specifically for increased 

 egg production, but the parallelism does not necessarily mean that the 

 latter has caused the former. It is noticeable that the broody periods 

 are fewer in number and limited to the height of the broody season in 

 many individuals, which afterward may become regular producers, with- 

 out further evidence of broodiness in that season. For example, instances 

 are quite common where a single broody period occurs in mid-season, 

 and is followed by continuous production, as shown in Fig. 3. Sometimes 

 there are two or even three such periods followed by continuous produc- 

 tion. Occasionally some birds have broody periods occurring at rather 

 irregular intervals. 



When birds are kept through the second season it is found that some 

 birds that did not become broody the first season may become broody 

 at some point in the second season. One instance occurred where the 

 bird did not become broody till the third season. Because of the physical 

 limitations in the matter of plant equipment we are unable to give the 

 exact percentage of birds not broody in their pullet year that became 

 broody later on. We have, of course, the data for such birds as were 

 kept over, but we do not believe it gives a fair picture of what will be found 

 in large flocks. They are, however, fairly numerous. There is, moreover, 

 some evidence that various lines behave unlike others in this respect. 

 On the other hand, only four instances free from complications have 

 occurred among our records of birds that were broody the first season 

 but failed to become broody thereafter. It is clear that the pullet 3'ear 

 is a good index of the presence of the broody instinct for those birds that 

 actually become broody, but not as good an index for those that do not 

 become broodj''. 



This brief description of variation in amount of broodiness, together 

 with the data given in Table VIII, is sufficient to give the reader a general 

 idea of its nature. Further details are outside the scope of this paper. 



