WINTER CYCLE AND WINI'ER I'AUSE 



175 



Number of liirds .... 



Mean liatehing date (Apr. 17) 



Hatdiinjr date standard deviation 



Mean length of winter pause 



Winter pause standard deviation 



Coeftieient of correlation 



Regression of hatching date on winter pause 



Regression of winter pause on hatching date 



The mean length of the winter pause over the entire nine-year period 

 amounts to 32.26 days for the pause birds, but a striking fluctuation in the 

 duration of the pause is revealed by its standard deviation. Environmental 

 influences may be considered as largely responsible for the fluctuations. Any 

 jiossible changed environment to shorten the pause would be advantageous 

 economically. 



The coefficient of correlation measuring the degree of association between 

 time of hatching and duration of winter pause is negative, of moderate 

 magnitude, and certainly significant. Clearly, a reduction in the range of 

 hatching dates would tend to reduce the length of the period of non-produc- 

 tion during the winter season. The mean length of winter pause of the eight 

 different hatches studied follows: 



Hatches 

 I 

 2 

 3 



4 



5 

 6 



7 

 8 

 Grand Average 



No. of Birds 

 353 

 271 

 293 

 289 

 261 

 245 

 227 

 195 



Mean days Paused 

 39.41 

 37.35 

 36.46 

 33.84 

 28.22 

 25.99 

 25.85 

 24.32 

 32.26 



S. Correlation ]Jeticeen Hatching Date Earlier Than The Mean and the 

 Presence of Winter Pause For Entire Population. 



Yule's short method as cited by Davenport (1907) is used in this study. 

 This tabulation includes the total population, 337.5 Rhode Island Reds classi- 

 fied as pause and non-pause individuals. 



Coefficient of correlation 



-f.2326± .0110 



