VARIABILITY IN EGG WEIGHT 7 



Correlation Between Annual Variability in Egg Weight and Winter Clutch Size 



Winter clutch size is a good measure of intensity, as was pointed out by Hays 

 and Sanborn (1927, 1932). Data have also been presented (Hays and Sanborn, 

 1927) showing that winter clutch size behaves as an inherited character. The net 

 correlation between winter clutch size and annual egg production is also very 

 significant, .4944 ± .0101 (Hays and Sanborn, 1927a), making this a very im- 

 portant character to breed for. 



The correlation between annual variability in egg weight and winter clutch 

 size will indicate whether or not the rate of laying affects the variability in egg 

 weight. The following constants were calculated: 



Number of birds 419 



Mean annual variability in egg weight, grams 2.81 



Standard deviation of annual variabilitx' + 1.00 



Mean winter clutch size, eggs 2.99 



Standard deviation of winter clutch size +1.23 



Coefficient of correlation —.0584 ± .0328 



The mean annual variabilit>- in egg weight between the twelve months was 

 2.81 grams. There is, however, a considerable variation here as shown bv a 

 standard deviation of 1.00. 



Mean winter clutch size of the population was 2.99 eggs, which places most of 

 the population in the high intensity phenotype. The variability of the population 

 with respect to clutch size was very high, amounting to about 40 percent as 

 measured by the coefficient of variation. This conforms to previous observations 

 that intensity as measured by winter clutch size is extremely variable. 



The coefficient of correlation between annual variability and winter clutch 

 size was very small and amounted to less than twice its probable error. Regres- 

 sion was tested and found to be linear, so that the data indicate no relation be- 

 tween the winter rate of laying and the variability in egg weight between the 

 months. 



Correlation Between March Variability in Egg Weight and Winter Clutch Size 



As previously pointed out, variability in egg weight was at a low level in the 

 month of March. The maximum egg weight of the first laying year also appeared 

 in March, making this month a good time to record the egg weight for the flock 

 as a whole. It seems desirable, therefore, to determine the correlation between 

 March variability in egg weight and winter clutch size. The following are the 

 resulting constants: 



Number of birds 750 



Mean March variability in egg weight, grams 2.05 



Standard deviation of March variability +.75 



Mean winter clutch size, eggs 3.12 



Standard deviation of winter clutch size + 1.24 



Coefficient of correlation —.0509 + .0246 



Regression of March variability on winter clutch size was found to be linear. 

 The correlation between March variabilit\- in egg weight and winter clutch size 

 was of such small magnitude as to be insignificant. This fact indicates that the 

 variability in egg weight for the month of March is not associated with differ- 

 ences in the rate of laying during the winter season. 



