VARIABILITY IN EGG WEIGHT 9 



Relation of March Variability in Egg ]]'eight to the Broody Instinct 



The mean March variability in egg weight for 18 broody birds was .87 grams 

 with a standard deviation of .097; the figure for 568 non-broody birds was 

 .72 + .015 grams. There was a difference of .15 + .097 grams which has no sig- 

 nificance. These data furnish some evidence that variability in egg weight at 

 any time of year is not affected by the broody instinct. 



Correlation Betiveen Annual Variability in Egg Weight and Persistency 



Hays (1927, 1936a) has shown high persistency to be inherited and to depend 

 in inheritance upon a single dominant gene. Hays and Sanborn (1927a) showed 

 high persistency to be the most important single inherited character affecting 

 egg production. Kno.x, Jul! and Quinn (1935) also found that high persistency 

 was the most imf ortant character affecting egg production. Lerner and Taylor 

 (1937) considered age at last egg to be the best measure of persistency and per- 

 sistency the most important character affecting annual egg production. 



It is obvious, therefore, that high persistency is one of the most desirable char- 

 acters to breed tor; hence it is important to know whether variability in egg weight 

 is in any way related to the length of the laying year. 



The correlation between annual variability in egg weight and length of the 

 first laying year was determined, giving the following constants: 



Number of birds 393 



Mean annual variability in egg weight, grams 2.85 



Standard deviation of annual \ariability +.99 



Mean persistency, days 346.48 



Standard deviation of persistency +33.60 



Coefficient of correlation —.0217 ± .0340 



The mean persistency was about 346 days, with a standard deviation of about 

 34 days. This is a rather small variability for a character of this nature and 

 indicates that high persistency was very well established in this population. 



The coefficient of correlation was negative and of no significance even though 

 regression was linear. These data indicate that variability in the length of the 

 laying year is not associated with annual variability in egg weight. 



Correlation between Alarch Variability in Egg Weight and Persistency 



For the purpose of studying variability in egg weight within a month in rela- 

 tion to persistency, the month of March has been chosen. The correlation be- 

 tween March variability in egg weight and persistency was determined, and gave 

 the following: 



Number of birds 586 



Mean March variability in egg weight, grams 2.05 



Standard deviation of March variability +.73 



Mean persistency, days 343.54 



Standard deviation of persistency +32.98 



Coefficient of correlation - .0537 + .0278 



Correlation ratio .1956 



Regression of March variability on persistency was non-linear, so that the 

 correlation ratio measures the association. The correlation ratio is of the negative 

 order and has a value of about .20 which means that onlj' about 4 percent of the 

 March variability in egg weight can be associated with variability in the length 

 of the laying year. 



