Sufferings of Birds 



of the almost incessant noise associated with 

 these establishments, the birds in general did 

 not seem to avoid them. It was, however, 

 recorded that two large ancient ROOKERIES, 

 one about a quarter and the other half a mile 

 away, were deserted in 1915 on account of a 

 field being used habitually for the descent of 

 aeroplanes (Observer, s.ix.is). 



Sound-waves of great explosions have been 

 found to travel long distances from the centre 

 of the disturbance. When the Silvertown 

 munitions factory exploded in East London 

 on January igth, 1917, it was heard 128 miles 

 away (Proc. Roy. Soc. Edin., vol. xxxviii. 

 p. 115), and other great explosions have been 

 distinguished at distances varying from 90 

 to 186 miles (Nature, 1917, p. 439). A limited 

 number of observations tend to show that 

 throughout a large part of the area over 

 which the sound-waves are audible, birds are 

 affected by the disturbance. The immediate 

 cause of their disquiet is unknown, but it is 

 supposed to be due either to actual percep- 

 tion of the sound of explosions or to shock 

 caused by air-wave concussion (Scottish 



