Ij^^ TECHNICAL BULLETIN 8 



(c) The Absolute Relationship of Winter Pause to Egp 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, 1921.), it is desirable and necessary to know some- 

 thing of the 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 this 

 report shows. The correlation between size of winter clutch and winter egg 

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

 egg record, and finally the correlation between winter pause and annual pro- 

 duction is studied. 



2S. Correlation Bet-iveen Size of Winter Clutch and Winter Egg Yield. 



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

 sidered in sections 17 and 18. In this section the 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 available on 3376 birds 

 upon which the following constants were ascertained: 



Number of birds 3376 



Mean size of winter clutch ...... 2.51 



Winter clutch standard deviation .... ±1.23 



Mean winter production ...... 61.08 



Winter production standard deviation . . . ±2.5.79 



Coefficient of correlation ...... -)-. 472.5 ± .0090 



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



Regression of production on winter dutch . . -)-9.884 



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

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

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

 winter cycle is determined by a four-day pause before Marcii first while 

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

 ord is highly variable on account of the complexity of its inlieritance. 



The magnitude of the above correlation coefficient emphasizes an important 

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

 terion of winter fecundity large clutch size is very important. 



2^. Correlation Betxveen Length of Winter Pause and Winter Egg Record. 



Winter pause represents a definite period of non-production, but the tend- 

 ency of winter pause and winter production to move in o})posite directions 

 <an only be measured by means of the coefficient of correlation. Tlie group 

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

 ing are tlie constants obtained: 



\i 



