8 MASS. EXPERIMENT STATION BULLETIN No. 286 



associated with variance in persistency is only .0133 and is far too small to be 

 of significance. These data, therefore, point to no association between the four 

 inherited traits considered and April clutch size. 



May Clutch Size 



Table 1 shows no significant correlation between May clutch size and the 

 three inherited characters, age at first egg, winter pause duration and total days 

 broody. The correlation coefficient of +.1122 + .0163 between May clutch size 

 and persistency is of very small magnitude and of little significance. Blakeman's 

 test shows that the relation between May clutch size and the four inherited traits 

 is linear. The general statement seems justified; that clutch size during the three 

 spring months is practically independent of the four inherited characters con- 

 sidered essential to high annual egg production. 



Summer Clutch Size 



The period from June first to the end of the 365-day laying year is often a 

 period of low production in improved flocks. During this time mortality is 

 likely to be high, many birds may stop laying because of broodiness, others lay 

 at a low rate and still others do not persist in laying to the end of their j^ear. 

 Information regarding the possible relation of clutch size at this season to in- 

 herited fecundity traits should be of considerable value. 



Table 1 indicates by means of the insignificant value of r, that age at first 

 egg and summer clutch size are independent. The same relation has already 

 been indicated between age at first egg and spring clutch in contrast to a signi- 

 ficant value of -.7475 between age at first egg and winter clutch size. 



There is a small non-linear correlation between duration of winter pause and 

 summer clutch size. The value of the constant is +.1678 indicating to a small 

 degree the tendency for a long winter pause to enable the bird to lay at a slightly 

 higher rate in summer. 



Regression of days broody on size of summer clutch is non-linear and positive. 

 The correlation ratio .3531 gives the true relation. This value is of considerable 

 significance and indicates that the inter-broody periods tend to be periods of 

 heavy laying. This agrees with the previous observation that winter pause dura- 

 tion is correlated with size of spring clutch. These data indicate that a period of 

 non-production is likely to be followed by large clutches. 



Persistency does not show a linear regression on summer clutch size. Using 

 the correlation ratio to express the correlation, the positive value .2078 is ob- 

 tained. Such a constant shows that intense layers tend to a small degree to be 

 persistent layers. 



In general, the study of the relations of six short-time measures of intensity 

 to inherited characters affecting fecundity shows the following significant corre- 

 lations: Winter clutch and early se.xual maturity, spring clutch and duration of 

 winter pause, summer clutch and duration of winter pause, winter clutch and 

 days broody, summer clutch and days broodj'', winter clutch and persistency, 

 spring clutch and persistency and summer clutch and persistency. 



