192 TECHNICAL BULLETIN' 11 



RELATION OF AGE AT FIRST EGG, BROODINESS, AND INTENSITY 



Age at first egg has previously been shown to be an inherited trait 

 (Hays, 1924), and to be intimately correlated with fecundity (Hays and 

 Bennett, 1923) in the Rhode Island Reds being studied. It is desirable 

 to discover if age at first egg and degree of broodiness are dependent or 

 independent. 



17. Correhtfioti Between Acje at Firtit Eijg and Total Days Broody. 



The broody population for the ten-year period has been tabulated in 

 a correlation table for age at first egg and total days broody during the 

 pullet year. Constants obtained are as follows: 



Number of birds 1207 



Mean age at first egg 207.76 



Age standard deviation ±31.52 



Mean total days broody 42.81 



Days broody standard deviation ±27.41 



Coefficient of correlation +.0062 ±.0194 



The magnitude of the coefficient correlation between age at first egg 

 and total days broody is insufficient to indicate any correlation between 

 age at first egg and degree of broodiness. Because of this fact it is very 

 probable that these two inherited characteristics are in no way linked in 

 inheritance. 



Age at first egg has been shown in sections 4 and 6 of this report to be 

 rather intimately correlated with winter intensity. Apparently there is 

 linkage between the genes E and E' for early maturity and genes I and I' 

 for large clutch size. Tlie degree of linkage has not been determined as 

 yet. 



18. Correlatidii Betiveeu Total Dayts Broody and Mean Winter Clutch Size. 



Hays and Sanborn (1926a) report no significant correlation between 

 degree of broodiness in the broody population and net winter rate of lay- 

 ing. Since mean winter clutch size is a useful measure of intensity, it is 

 desirable to ascertain if the degree of broodiness is correlated with mean 

 winter clutch size. The following constants liave been calculated for the 

 broody population over the ten-year period: 



Number of birds 1188 



Mean total days broody 42.89 



Days broody standard deviation ±27.54 



Mean winter clutch size 2.96 



Clutch size standard deviation ±1.38 



CoeQicient of correlation +.2205 ±.0186 



In section 3 the mean winter clutch size of both broody and non-broody 

 birds is 2.64. The mean winter clutch size of the broody birds alone is 

 found to be 2.96. This fact suggests that, on the average, broody birds 

 tind to lay in larger clutches during the winter than do non-broody birds. 



The coefficient of correlation between total days broody and mean win- 

 ter clutcii size is statistically significant, and suggests that degree of 



