WINTER PAUSE IN RHODE ISLAND REDS 7 



In the group of 353 birds that completed their first laying year, there was 

 the rather high mean of about 141 eggs following the winter pause. The re- 

 gression of pause duration on subsequent egg production was nonlinear. The 

 correlation ratio of .2377, therefore, expresses the true relation. There was 

 something of a tendency for birds with short pause to lay more eggs for the 

 remainder of the year than did the birds with long pause. This further sub- 

 stantiates the idea that winter pause cannot be considered as a recuperative 

 period enabling the pullet to begin laying at a higher rate than her nonpause 

 sisters. 



9. Winter Egg Production and Pause Duration 



Since a cessation of laying between November 1 and March 1 actually 

 shortens the period of winter production which ends March 1, winter pause 

 birds are certain to lay fewer winter eggs than nonpause birds unless these 

 pause birds are earlier maturing and lay at a higher rate to compensate for 

 the time lost. The mean age at first egg was 190.30 days for the pause group 

 of 693 birds and 194.95 days for the 313 nonpause birds. Mean winter clutch 

 size was 3.21 eggs for the 693 pause birds and 4.02 eggs for the 313 nonpause 

 individuals. These facts show that winter pause actually represents a pro- 

 duction loss dependent upon its duration. The coefficient of correlation was 

 calculated between pause duration and winter egg production, giving the 

 following constants. 



Number of birds .... 

 Mean winter production, eggs 

 Production standard deviation, eggs 

 Mean pause duration, days . 

 Pause standard deviation, days . 

 Coefficient of correlation 



693 



78.95 



+ 26.10 



37.11 



±24.31 



-5606± .0176 



Mean winter egg production of the pause group was 78.95 compared with 

 102.94 eggs for the 313 birds without pause. The actual time loss was 37 days 

 for the pause birds, and in the nonpause group each bird averaged to lay 24 

 eggs more. 



The regression was found to be linear and the correlation coefficient was 

 negative and of considerable magnitude. By squaring the coefficient of cor- 

 relation it was found that about 31 percent of the variation in winter egg 

 production was due to variation in pause duration. The fact is very obvious, 

 therefore, that winter pause represents a distinct economic loss in winter egg 

 production. 



10. Mean Winter Body Weight and Pause Duration 



Beginning with the flock hatched in 1934, monthly individual weights of all 

 birds have been taken starting with the day they were housed. The birds 

 were housed at about six months of age and the mean winter body weight repre- 

 sents the average of the monthly weights beginning with the housing weight 

 and concluding with the February weight. It is desirable to know whether 

 body weight affects either the presence or duration of winter pause. The 

 correlation coefficient has been calculated on 322 pause birds hatched in 1934. 

 Body weight has also been recorded on 244 nonpause individuals in the same 



