HKOODINI'.SS AND FI'.ClN Dll ^ 1\ l-()\\l. 75 



;ird tk'vi;ilimi in times lirootly is jiivalrr tli.ui liic iik'.iii lu'taiisr !).')1 hirds (H;J 

 JUT cent) fell into classes 1-4, Icavinir only 17 jxt cent in classes H-lli. Tiic 

 iiuulal class is 'J. 



The mean lenglli of Ijroody jjcriods is 15.10 days witli a standard deviation 

 of ± 3.78. There is, therefore, much {greater uniformity in len^lli of period 

 than is observed for number of periods. Evidently the numiu-r of i)eriods 

 otVcrs a more fertile held for imi)rovement than is offered by the lenfrth of 

 period. 



The negative coetticient of correlation indicates tiiat an increase in numi)er 

 of broody periods is accompanied by a decrease in tiieir average length. A 

 reduction in number of periods would therefore be accompanied by an increase 

 in their length. That this relationship is far from absolute is shown by the 

 magnitude of the correlation coetticient. Certainly the time lost in non-pro- 

 duction has been very significantly reduced by decreasing the innnber of 

 broody periods, as table 1 shows. 



.'.). Correlation Between Winter Rate and Annual Rate — Pullet )'ear. 



The records for 2212 individuals both broody and non-broody are available 

 for study. This relationship is important liecause both rates bear ;i rather 

 intimate relation to egg production. The fact has previously been pointed 

 out that broody birds tend to be more intense winter layers than are non- 

 broody birds, but that the former are likely to carry a lower annual rate. An 

 intimate correlation between winter rate and annual rate would suggest that 

 rate of laying for the year may be predicted from the winter rate. Constants 

 calculated are as follows: — 



Number of birds ....... 224.2 



Mean winter rate ....... 66.41 



Winter rate standard deviation .... ±.9.38 



Mean annual rate ....... 56.46 



.Vnnual rate standard deviation .... ±9.85 



Coefficient of correlation +.4900 ± .0108 



The above con.stants indicate a slightly greater relaLive standard deviation 

 in annual rate than exists for winter rate. Such a condition might he sur- 

 mised from the fact that broodiness and complete molt may both affect anmial 

 rate but for the most i)art are not concerned in winter rale. 



A rather intimate correlation exists between winter and annual rate. Evi- 

 dently those birds above the average in winter rate would be exi)ected to be 

 above the average in annual rate. The practice of selecting for high winter 

 rate is without doubt sound from the standpoint of securing high annual rate. 



J4. Correlation lietween the Presence of Broodiness and Winter Production 

 above the Mean of Broodies and Non-ljroodies Comfrined — Pullet Year (Flocks 

 1916-1923). 



The absolute correlation !)et\veen the presence of l)r()odine.ss and winter ))ro- 

 duction above the mean of all birds is of much concern to poultrymen striving 

 for high winter records. Such information will show whether or not itroody 

 birds tend to lay more eggs before March first than do broody-free birds. In 

 section 8 some evidence is presented to indicate that broody birds do actually 

 lav at a .slightly higher rate than non-broodies when they are laying; but late 

 J...... .pi pinturitv, winter, pause and the occasional winter l)roody ])eri(td may 



