36 BRITISH BIRDS. [vol. xtii. 



two or three abortive efforts. On the night of June nth 

 booming was continuous from 8.0 p.m. (solar time) until 1.30 

 a.m. It was one of the brightest and stillest nights I have 

 ever known. Bitterns challenged each other unceasingly 

 and sometimes the boom of one bird overlapped that of 

 another. No two birds seemed to boom in exactly the 

 same key. One far-away Bittern's voice was decidedly 

 high pitched. Distance and atmospheric conditions may 

 partly account, perhaps, for these variations in tone, but 

 they are, nevertheless, as individual as are the lowings of 

 different cows. 



