INTENSITY IN RHODE ISLAND REDS 5 



4. Mean Winter Clutch Size and March Egg Weight 



It is also desirable to know if winter clutch size is related to March egg weight. 

 Records are available on 612 birds whose eggs were weighed during March. The 

 following constants appeared: 



Number of birds 612 



Mean winter clutch size — eggs 3.25 



Clutch size standard deviation +1.31 



Mean March egg weight — grams 60.54 



Egg weight standard deviation + 3.95 



Coefficient of correlation — .1219 + .0269 



Regression of egg weight on winter clutch size was linear. The correlation 

 between winter clutch size and March egg weight was — .1219 ± .0269 and is 

 significant. It is apparent, therefore, that in selective breeding for high winter 

 intensity care must be taken to maintain egg size at a satisfactory level. 



5. Mean Winter Clutch Size and Annual Egg Weight 



Annual egg weight as used here represents the mean of twelve monthly means 

 obtained by weighing every egg as taken from the trapnests. Such records are 

 available on 430 females. The following are the constants calculated: 



Number of birds 430 



Mean winter clutch size — eggs 3.17 



Clutch size standard deviation ± 1.33 



Mean annual egg weight — grams 58.51 



Egg weight standard deviation ±3.79 



Coefficient of correlation — .0748 ± .0343 



The coefficient of correlation is negative but is of such small magnitude as to 

 be insignificant. Regression was strictly linear. 



These data indicate that birds may be selectively bred for high winter in- 

 tensit\- without influencing mean annual egg weight. 



Relation of Egg Production to Egg Weight 



6. Winter Production and Winter Egg Weight 



Winter production of eggs from the first pullet egg up to March 1 is something 

 of a measure of intensity of laying even though it is greatly influenced by age at 

 first egg and b>- winter pause duration. The number of eggs laid before March 1 

 may be paired against the mean egg weight up to January 1. This procedure was 

 followed, using 1463 individual pullet records to derive the following constants: 



Number of birds 1463 



Mean winter production — eggs 91.12 



Winter production standard deviation . . ± 24.98 



Mean winter egg weight — grams 54.96 



Egg weight standard deviation ± 3.88 



Coefficient of correlation — .1593 + .0172 



Correlation ratio .1915 



