4 MASS. EXPERIMENT STATION BULLETIN 416 



age at first egg and winter clutch size. Hays and Sanborn (1927b) found the 

 partial correlation between age at first egg and winter clutch size to be —.1879 

 ± .0105. Knox, JuU and Quinn (1935) reported no significant correlation be- 

 tween age at first egg and percentage production to March 1 in either Rhode 

 Island Reds or White Leghorns. Lerner and Taylor (1937) found a very low 

 correlation between age at first egg and net winter rate of laying in White Leg- 

 horns.' 



A population of 1470 birds was used in this study, and the following constants 

 were obtained: 



Number of birds 1470 



Mean age at first egg — days 189.82 



Age standard deviation + 16.43 



Mean winter clutch size — eggs 3.23 



Clutch size standard deviation + 1.42 



Coefficient of correlation. .- — .0921 + .0174 



Correlation ratio -.1398 



The above data show that the birds used for stud}' were extremely variable 

 in winter clutch size. The standard deviation divided by the mean gives a co- 

 efificient of variation of 43.9 percent. Blakeman's test showed that the regression 

 of clutch size on age at first egg was not strictly linear. The correlation ratio 

 .1398, therefore, expresses the association, which is of a negative order and is 

 statistically significant. This correlation is less intimate than was observed in 

 earlier generations but does indicate that earlier maturing females are likely to 

 be more intense layers than later maturing individuals. It should be noted that 

 the population included only 53 birds that matured at 220 days or older. 



Relation of Winter Intensity to Egg Weight 



3. Winter Clutch Size and Winter Egg Weight 



Hays (1930b) pointed out that a gene A for small egg size is probably linked 

 with gene I' for highest intensity. Since that time gene A has been largely 

 eliminated from the flock so that large egg size prevails (Hays, 1944). It may be 

 anticipated, therefore, that high winter intensity will be less intimately correlated 

 with small egg size than in earlier generations of the flock. 



A population of 1463 pullets hatched from 1937 to 1942 was tabulated for 

 study, with the following results: 



Number of birds 1463 



Mean winter clutch size — eggs 3.23 



Clutch size standard deviation + 1.42 



Mean winter egg weight — grams 54.96 



Egg weight standard deviation ± 3.88 



Coefficient of correlation — .1383 ± .0173 



Mean winter egg weight was determined from the weights of all eggs laid from 

 the first pullet egg up to January 1. Regression of egg weight on clutch size was 

 strictly linear. The coefficient of correlation was — .1383 ± .0173. This is a 

 significant though not intimate correlation and shows that rapid laying does tend 

 to reduce egg size. 



