WATCHING BIRDS AT A STRAW-STACK 211 



forward as something difficult of explanation, and 

 many, perhaps, will doubt there being any such 

 difficulty in regard to a thing so ordinary and 

 commonplace. As to this, I can only say that I 

 have arrived at a different conclusion. 



What would be the ordinary way of accounting for 

 such sudden and simultaneous taking to flight of a 

 number of birds? One may suppose, in the first 

 place, that a particular note is uttered by one or 

 more of them on the espial of danger, and that this 

 acts as a sauve qui peut to the rest. This seems a 

 satisfactory explanation, but as against it, no such note 

 is, as a rule, uttered, and even if it were, it would not 

 account for all the facts as I have often observed them. 



Day after day, and for hours at a time, I have 

 watched these crowds of little birds under the circum- 

 stances described, and only on one single occasion 

 was the sudden rising into the air in flight preceded 

 by any note at all, nor did I observe anything — I do 

 not believe there was anything to be observed — which 

 could have frightened them. 



In the one case referred to, which was different, 

 " the flight was certainly preceded by a note — a very 

 peculiar one, single, long, and remarkably loud, taking 

 the size of the birds into consideration. It suggested 

 somewhat the sudden blowing of a horn — though, of 

 course, a small one. I could not tell which bird uttered 

 it, but feel sure, from the quality of the tone, that it 

 was a greenfinch. To the best of my observation, the 

 note was uttered before the flight commenced, and the 

 flight followed before it had ceased. Almost imme- 

 diately afterwards I heard, for the first time, the caw 

 of rooks, and my theory is (or was) that one of these, 



