182 TERRITORY AND REPRODUCTION 



in surroundings that afforded the customary 

 amount of protection from the elements, I made 

 a note of the temperature and the atmospheric 

 conditions and then observed the condition of 

 the young at frequent intervals. Details of 

 these experiments will be found at the end of 

 the chapter. 



The experiments with the Blackbirds and 

 the Whitethroats gave the most interesting 

 results. Both broods of each species were 

 respectively of much the same age, yet one 

 brood of Blackbirds survived for five, and the 

 other only for two and a half hours, and one 

 brood of Whitethroats lived for twelve hours 

 whilst the other succumbed in a little over an 

 hour. This difference is rather remarkable; 

 and it seems clear that the power of resistance 

 of the young diminishes rapidly when the 

 temperature falls below 52° F. It must be 

 borne in mind, however, that the conditions 

 under which the experiments were made were, 

 on the whole, favourable — the weather was dry, 

 the temperature was not unusually low, nor was 

 the wind exceptionally strong or cold ; and even 

 in those cases in which the young succumbed so 

 rapidly, the atmospheric XJonditions could by no 

 means be regarded as abnormal. 



What, then, would happen in an unusually 

 wet or cold breeding season ? For how long 

 would the young then survive ? In the spring 

 and early summer of the year 1916, I was 

 fortunate in observing the effect of exposure 

 under natural but inclement conditions. I 



