I30 



ANIMAL AGGREGATIONS 



winter at a time of relatively low egg production, when the nights 

 are becoming increasingly cold, the large crowded flocks apparently 



c,2 



J5 



-1 



/VOV. DEC. 



JAN 



r£B. MAR. AP/i. nAY JUNE JULY AUG. 6EPr 



Fig. 6. — Diagram showing the average excess in mean egg production of different 

 sized flocks of barred Plymouth Rock pullets in the first 1 1 months of their first year 

 of laying. 



, 50-bird pens compared with loo-bird pens. 



J 50-bird pens compared with 1 50-bird pens. 



, loo-bird pens compared with 150-bird pens. 



The broken lines running parallel with the zero line approximate the mean probable 

 error. Points below the zero line indicate that the larger number per pen gave a higher 

 average egg production. Points above the zero line show that the pen with the smaller 

 numbers gave the higher average. (From Pearl and Surface, 191 1.) 



conserve animal heat, so that greater egg-laying occurs in the more 

 crowded pens. Second, as the period of maximum egg production is 



