4 MASS. EXPERIMENT STATION BULLETIN 329 



duration has been calculated for the birds in this study. 



Number of birds . . . ... . . . 692 



Mean weight at first egg, pounds .... 5 . 90 



Weight standard deviation, pounds .... ± . 60 



Mean pause duration, days 37 . 14 



Pause standard deviation, days +24.32 



Coefficient of correlation +.0836 + .0255 



The mean weight was very satisfactory and the variation in weight was not 

 excessive, since the coefficient of variation was about 10 percent. The co- 

 efficient of correlation is so small that it indicates no significant relation be- 

 tween weight and pause duration. These data indicate that pullets that are 

 heavy when they lay their first egg are likely to pause just as long as lighter- 

 weight birds. Body weight at first egg cannot, therefore, be used as an indi- 

 cator of a pullet's probable ability to lay continuously throughout the winter. 



4. Time Interval Between Eggs and Winter Pause. 



The rate of laying depends in large measure upon the time interval between 

 eggs of the same clutch during any particular time, as Hays (1936) has pointed 

 out. It is desirable to know also whether the mean time interval between 

 eggs during the months from October to February of the pullet year shows any 

 relation to the presence or absence of winter pause or to pause duration in 

 birds with pause. Hourly trapnest records are available only on the flocks 

 hatched up to 1926; consequently the 1926 flock of 462 birds was chosen for 

 this study. 



The data for each of the five months considered are presented in table 1. 

 The table shows that the time interval between eggs increased through the 

 winter months from 25.78 hours in October to 27.43 hours in February. 



Table 1. — Time Interval Between Eggs and Winter Pause 



♦Only birds with pause included. 



Freedom from winter pause did not increase or decrease regularly with the 

 time interval change in any of the five months considered. There was, 

 however, a tendency for the more rapid layers to show a greater degree of 

 freedom from pause. The group of birds having a time interval of 25.5 hours 

 showed the highest percentage of nonpause birds in October and November. 

 In December the 64 birds with a time interval of 27.5 hours were freest from 

 winter pause; in January there was least winter pause in the 28-hour group; 

 and in February the highest percentage of nonpause birds was in the 26.5- 

 hour class. 



