MASS. EXPERIMENT STATION BULLETIN 423 



Number of birds with spring pause 356 



Mean spring pause — days 26.21 



Spring pause standard deviation ±26.61 



Mean annual production — eggs 184.42 



Annual production standard deviation ±41.77 



Coefficient of correlation —.3323 ±.0318 



Correlation ratio .4088 



The birds exhibiting spring pause were relatively low producers, with an average 

 of about 184 eggs. Another very striking fact is the immense variability in spring 

 pause duration. There is the suggestion that pathological conditions may have 

 produced many spring pauses, but there is no proof of this. A further possibility 

 might be physiological disturbances in some of the birds. 



Regression was non-linear, so that the correlation ratio .4088 expresses the 

 association. The magnitude of this constant shows that the length of the spring 

 pause is rather intimately associated with annual egg production and that it has 

 a somewhat greater effect than was observed for winter pause. 



10. Relation of Summer Pause Duration to Annual Production 



Summer pauses of eight or more days, not associated with broody behavior, 

 often occur in June, July, and August. Such pauses are of much more frequent 

 occurrence than spring pauses. In the population studied 749 individuals ex- 

 hibited summer pause. The possible association between the duration of sum- 

 mer pauses and annual egg production in the summer pause population has been 

 studied. The following constants appeared: 



Number of birds with summer pause 749 



Mean summer pause — days 40.64 



Summer pause standard deviation ±31.32 



Mean annual production — eggs 196.02 



Annual production standard deviation ±41.47 



Coefficient of correlation —.4629 ±.0194 



Correlation ratio. .4966 



There was a marked variability in the duration of summer pause. In this 

 group of birds production was mediocre, but superior to that of birds with spring 

 pause. Regression was non-linear, so the correlation ratio expresses the associa- 

 tion, which was more intimate than was observed for either winter or spring 

 pause. 



The duration of pauses in production in winter and in spring were about equally 

 important in relation to annual egg production. The variability in duration 

 of summer pause was more intimately correlated with annual production. On 

 the whole, these periods of non-production deserve very careful consideration. 



Broodiness 



11. Relation of Number of Broody Periods to Annual Production 



In the population of 1470 females, only 56 individuals or 3.8 percent exhibited 

 broody behavior during the first laying year. This group of 56 birds had a mean 

 annual egg production of 212.18 eggs compared with an average of 213.62 eggs for 

 the 1414 non-broody individuals. The average number of broody periods for the 

 broody population was 1.39 or the equivalent of about 21 productive days lost 

 for each individual. The broody population was shown to be superior to the 

 non-broody population in winter intensity. The respective clutch sizes were 3.81 

 and 3.20 days (Hays, 1944). 



