-j^g^ TECHNICAL BULLETIN 8 



(c) The Absolute Relafiottsh'p of W'mler Pause to E(j(i Production. 



The duration of winter pause may he considered a factor affecting 'the 

 number of eggs laid before March first as well as for the entire year. Since 

 winter fecundity alone depends upon the inheritance of seven pairs of 

 Mendelian factors (Hays, 192'i'), it is desirable and necessary to know some- 

 thing of tiie relation of winter pause to winter and annual egg record. Al- 

 though fecundity is very complex in its mode of inheritance, its manifesta- 

 tion depends in part upon environmental conditions as division (a) of tliis 

 report shows. The correlation between si/e of winter clutch and winter egg 

 yield is first considered, then the correlation between winter pause and winter 

 egg record, and finally tiie correlation between winter pjiuse and annual pro- 

 duction is studied. 



iio. Correlation Between Size of Winter Clutch and Wiuier Eijii Yield. 



The relation of winter clutch size to winter pause has already been con- 

 sidered in sections 17 and 18. In tliis section tlie relation of winter clutch 

 size and winter egg production are studied. Since size of winter clutch is so 

 often used as a criterion for selection by poultrymen, knowledge of its rela- 

 tion to winter fecundity is important. Records are avaiial)le on 3376 birds 

 tipon which tiie following constants were ascertained: 



N'unber of birds 3376 



Mean size of winter clutch ...... 2..57 



Winter clutch standard deviation .... ±L23 



Mean winter production ...... 61.08 



Winter production standard deviation . . . ±25.7 9 



Coefficient of correlation -^.472-5 ± .(J090 



Regression of winter clutch in production . . -|-.023 



Regression of production on winter clutcii . . -j-^-^*** 



The fact will be observed that tlic mean winter production above is greater 

 than the mean length of winter cycle given in section 6. The mean length of 

 winter cyolc is less than mean winter production because the end of the 

 v'iiiter cycle is determined by a four-day pause before March first while 

 winter egg record does not cease until February 28 or 29. Winter egg rec- 

 ord is highly variable on account of the coniplexity of its inheritance. 



The magnitude of the above correlation coefficient em})iiasizes an important 

 tendency for clutch size and winier production to move together. As a cri- 

 terion of winter fecundity large clutch size is very important. 



S//. Correlation Between Lenath of Winter Pan.se and ]V infer E(i(i Record. 



Winter pause represents a definite period of non-production, l)ut the tend- 

 ency of winter pause and winter production to move in opposite directions 

 can only be measured by means of the coefficient of correlation. The group 

 of 2134- pause birds has been tabulalfd to give this relationship. The follow- 

 ini>; are the constants obtained: 



