198 TECHNICAL BULLETIN 12 



Relation of Characteristics Concerned in Fecundity to Each Other 



1. Age at First Eyg and Length of Winter I'amte. 



Age at first egg may be definitely recorded and lias been used extensively 

 as a criterion of future productive ability. The simple correlation between 

 age at first egg and annual egg yield in these flocks is — .4380±.0134 (Hays 

 and Bennett 1923), liut this apparent correlation may be due to linkage re- 

 lations between early sexual maturity and other high fecundity traits. By 

 making intensity, days broody, and annual persistency constant, the net or 

 partial correlation between age at first egg and length of winter pause is 

 — .2236±.0139. Here is a significant correlation which suggests some link- 

 age between early sexual maturity and long winter pause. The relationship 

 is far from intimate, however, and probably does not signify that genetically 

 early-maturing birds need be handicapped by winter pause. 



2. Age at First Egg and Mean Size of Winter Clutch. 



The mean size of winter clutch is obtained by dividing the total eggs laid 

 from first egg to March first by the number of clutches involved. Clutch size 

 has been shown by Hays and Sanborn, (1927) to be a good measure of in- 

 tensity and behaves in inheritance on a two-factor basis. The simple correla- 

 tion between mean winter clutch size and annual egg yield is -}-.3.54.4±.0117 

 (Hays and Sanborn, loc. cit.). If early sexual maturity is linked with large 

 winter clutch size, there should exist a significant net correlation between the 

 two. The net correlation between age at first egg and mean winter clutch 

 size, after making the length of winter pause, total days broody, and annual 

 persistency constant, is - — .1879±.O105. This is a statistically significant con- 

 stant, but its magnitude does not suggest that early sexual maturity is in- 

 timately linked with high intensity. 



3. Age at First Egg and Total Days Broody. 



Total days broody during the pullet year is a good measure of degree of 

 broodiness (Hays and Sanborn 1926a). These workers also show in the same 

 report that degree of broodiness as well as the presence or absence of broodi- 

 ness during the pullet year must be considered in the breeding program. The 

 simple correlation between total days broody and age at first egg is-(-.0062 

 ±.0194, a constant of magnitude insuificient to indicate any relation between 

 early sexual maturity and days broody. By calculating the partial correlation 

 between age at first egg and total days broody where winter pause, intensity 

 and persistency remain constant, the true relation between sexual maturity 

 and degree of broodiness is arrived at. The partial correlation coeflFicient is 

 found to be -]-.0473±.0194, which establishes independence between age at 

 sexual maturity and degree of broodiness. 



4. Age at First Egg and Annual Persistency. 



Persistency or long laying period at the close of the pullet laying year is of 

 great significance as affecting annual egg production. Hays and Sanborn 

 (1926c) report the simple correlation between annual persistency and annual 



