WINTER CYCI.K AND WINTKK i'AL'SK 



170 



14. Vorrelat'uin Betxceen Body WeUjht at First E<j<j Loic'er Than tin- Mean 

 and the Preaence of Winter Panne for Entire Population. 



Coefficient of t-orrelation 



.0110 zii .0117 



The complete independence between weight at first egg and tiie presence 

 (»f winter pause is shown by the above correlation coelticient. Evidently 

 body weight is not a factor in either the manifestation of winter pause or 

 its duration. 



JS. Correlation Between Winter Rate and Length of Winter Pavne. 



The group of 2131- birds exhibiting winter j)ause is used in these calcula- 

 tions. Winter rate or intensity was calculated for each individual bird in 

 the following manner: — 



The total number of eggs from first egg to March first was divided by the 

 number of days from first egg to March first, less all pauses of four or more 

 days in duration from November first to March first. By this method of 

 calculation the actual net rate of laying is arrived at if the assumption is 

 correct that a cessation of laying for four or more days during winter actu- 

 ally constitutes a winter pause. A four-day cessation of laying may gener- 

 ally be assumed to necessitate the omission of one clutch of eggs for the 

 average bird and such omissions suggest the manifestation of winter pause. 

 The following constants were calculated: 



Number of birds .... 

 Mean winter rate .... 

 W^inter rate standard deviation . 

 Mean length of winter pause 

 Winter pause standard deviation 

 Coefficient of correlation 

 Regression of rate on winter pause 

 Regression of winter pause on rate 



2134 



65.69 

 ±8.74 



32.26 

 ±21.92 



—.1023 ± .0144 



—.041 



—.257 



The above mean winter rate expresses the net rate of laying of all birds 

 exhibiting winter pause. This rate of laying is compared in section 16 with 

 that of the total population and that of the non-pause group above. The 

 standard deviation for rate is of moderate magnitude compared with the 

 standard deviation of many other fecundity characteristics. 



A small but significant negative correlation suggests a very moderate tend- 

 ency for high-rate birds to pause for a shorter period than do low-rate birds. 

 Such a relationship is important from the breeding standpoint in that it 



