200 TECHNICAL BULLETIN 12 



coefficient is — .0393±.0183 and indicates complete independence between dura- 

 tion of winter pause and annual persistency. 



8. Mean Winter Clutch Size and Total Days Brood;/. 



Broody birds exhibit some tendency to lay in longer clutches during winter 

 than do non-broody birds. Stated diflFerently, there is a somewhat higlier 

 winter intensity in broody than in non-broody individuals (Hays and Sanborn 

 1927). 



The net correlation between winter clutch size and total days broody for 

 the pullet year is -j-.2079±.0187. There are, however, many non-broody in- 

 dividuals showing large clutch size and these birds should be used as breeders 

 in the production flock. 



9. Mean Winter Clutch Size and Persistency. 



Both large clutch size and high persistency are desirable from the stand- 

 point of fecundity. They should be combined in the same individual to secure 

 maximum egg production. The net correlation between winter clutch size 

 and persistency when age at first egg, winter pause duration and total days 

 broody are made constant is -j— Ol^^— •*51*^- Thus complete independence is 

 established between intensity and persistency. 



10. Total Days Broody and Annual Persistency. 



Degree of broodiness may be measured by tlie total days spent in broody 

 behavior during the pullet laying year. The loss of production during broody 

 periods has a pronounced eflFect in lowering annual egg records. On the other 

 hand, high persistency is associated with large annual records. The net cor- 

 relation between total days broody and annual persistency where age at first 

 egg, intensity and winter pause are made constant is -f-.0579±:.0209. Thus 

 there is shown to be no significant linkage between degree of broodiness and 

 annual persistency. 



Relation of Characteristics Concerned in Fecundity to Annual Production 



In this final study of the relation of characteristics concerned in fecundity 

 to annual production the relative net correlation of each of the five traits with 

 annual egg record is calculated. In this manner the true value of each trait 

 as a selection unit may be discovered, as the method of partial correlation 

 eliminates any possible effects from interrelation of characteristics concerned. 



11. Age at First Egg and Annual Production 



Age at first egg is a good measure of early or late sexual maturity in the 

 pullet and has been used rather extensively as a selection unit in making up 

 both laying and breeding flocks. The reason why early sexual maturity is 

 desirable cannot be discovered without a knowledge of the relation of sexual 

 maturity to the other fecundity traits as presented in sections 1, 2, 3, and 4 

 of this report. The possibility also exists that pullets that begin laying at an 

 early age are able to complete their annual record under more favorable 

 weather conditions than are later maturing pullets. Since the last two or 



