BROODINESS IN DOMESTIC FOWL. 115 



its large probable error, is not significant statistically, but, ignoring the 

 error, may perhaps indicate that broodiness is an advantage, since, on 

 the average, those birds spending the most time in broodiness are the 

 heaviest layers. On the contrary, it is known from a study of other data 

 that the very best layers cannot spend much time in broodiness. The 

 interpretation we give this value is that those birds whose laying year 

 begins earliest and stops latest get in more broody periods, other things 

 being equal, than birds whose laying year is shorter. 



If an index of production of high value is desired, it is found in the 

 initial laying period, for here the correlation between the length of the 

 period and number of eggs produced is very high, viz., +.8843 i .0210, 

 a value, moreover, that indicates good homogeneity in rate of production 

 in this flock. 



In this flock there is a pronounced negative correlation between egg 

 production during the laying periods and number of broody periods, the 

 coefficient of correlation being — .3453 i .0716, indicating that those birds 

 that are very broody tend to lay less eggs between broody periods than 

 those having a less number of broody periods. On the other hand, there 

 is no relation between the average {i.e., for one individual) length of laying 

 periods or the eggs produced in such periods and average length of broody 

 periods, since in the fii-st case r = — .0130rt .0818', and in the second case 

 r = —.0013 ±.0818. 



While the above statements hold true for average values, if the coeffi- 

 cient of correlation is determined between the length of a laying period 

 or its egg production and the length of the broody period immediately 

 subsequent thereto, a marked negative correlation is found, being ■ — .2899 

 rt .0415 in the first instance, and —.3715 +.0345 in the second. The 

 disagreement between the values obtained when each laying period is 

 correlated with its subsequent broody period, and that found when the 

 average value for each bird is used, is due to a shortening of the laying 

 period and a lengthening of the broody period as the season progresses. 

 This is clearly shown on the individual records. 



If, instead of taking a laying period and its subsequent broody period, 

 a broody period is paired with the laying period following, little or no 

 relationship is indicated, for r between length of broody period and sub- 

 sequent laying period is — .0222 + .0388, while between length of broody 

 period and subsequent egg production it is only slightly greater, being 

 —.0799 ± .0372. 



The interrelationships discussed in the two paragraphs preceding may 

 perhaps be interpreted to mean that heavy laj'ing tends to suppress 

 broodiness, or, at least, that in the flock studied, those birds that laid 

 most heavily had shorter broody periods than those laying less heavily, 

 the tendency to hea\'y production in such birds enabling them to get 

 back more quickly into production than those in which the tendency 

 was less strong. Longer broody periods, however, and their accompany- 

 ing element of rest did not conduce to heavier production, a view con- 

 trary to that held by most poultrj-men. 



