WINTER CYCLE AND WINTER PAUSE j^-j'g 



Winter Pause 



In tlie following table are given the number of pause and non-pause birds 

 by years, together with the percentage of birds in the pause class. 



Year 



1916 

 1917 

 1918 

 1919 

 1920 

 1921 

 1922 

 1923 

 1924 



The average length of pause for those birds pausin 



1916 flock 

 1921 flock 

 1924 (lock 



6. Correlation Between Leiujth of Winter Ci/rle and Length of Winter Pause. 



The range in cycle length was found to be from 5 days to 175 days. The 

 class interval used was 10 days. Since winter cycle and winter pause are 

 complementary to each other, it is important to discover their possiijle rela- 

 tion to each other. The cocllicient of correlation will illustrate any tendency 

 for length of winter cycle and length of winter pause to move in the same or 

 in opposite directions. Such information will make clearer their physiological 

 relationships and possible genetic linkage. 



Number of birds ...... 



Mean length of winter cycle 



Length of winter cycle standard deviation . 



Mean length of winter pavise 



Length of winter pause standard deviation 



Coefficient of correlation .... 



Regression winter cycle on pause 

 Regression pause on winter cycle 



2078 



.52.26 

 ±34.23 



31.91 

 ±21.68 



—.1385 ± .014.5 



—.219 



—.088 



The length of winter cycle as measured in these studies is subject to wide 

 fluctuation as indicated by the relative magnitude of the mean and its stand- 

 ard deviation. Such fluctuations are to be anticipated in a population highly 

 variable for the seven pairs of inherited factors concerned in winter produc- 

 tion, subjected to uncontrollable variation in environmental influences. The 

 fact should be observed, however, that the mean length of winter cycle is 

 about 63 per cent greater than the mean length of pause. 



A small negative correlation coefficient indicates a very slight tendency for 

 long-cycle birds to pause for a shorter period than do short-cycle birds. This 



