212 BIRD WATCHING 



appearing suddenly in the air from the back of the 

 hay-stack, had been mistaken for a hawk, and that the 

 bird so mistaking it had immediately uttered the 

 appropriate warning note. Unfortunately for my little 

 mouse " (" theories," says Voltaire, " are like mice ; 

 they run through nineteen holes, but are stopped by 

 the twentieth"), "only the other day, when I was at 

 the same place and equally near, a genuine hawk (a 

 sparrow one) had flown by, when, instead of a warning 

 note, there had been a sudden hush and silence, fol- 

 lowed by a flight which, as it seemed to me, was not 

 so close and compact as usual. Difficulties of this sort 

 are always occurring in observation at least in my 

 observation and show how cautious one should be 

 in translating the particular into the general. For 

 instance, with moor-hens, I have noted that in one or 

 two of their many timorous flights to the river a 

 peculiar cry was uttered by a single bird, which had 

 all the appearance and seemed to have all the prob- 

 ability of being a warning note ; but this was not the 

 case on other occasions." Even here, then, there is 

 some difficulty in accepting the theory of a danger- 

 signal uttered by one bird, and causing the simul- 

 taneous flight of all, whilst in all other instances (I 

 am speaking now of small birds at the stacks) either 

 no note at all or none distinguishable from a general 

 chirping was uttered. Manifestly,* then, this explan- 

 ation will not serve. But it may be said, either that 

 there is a leader whose movements all the birds follow, 

 or that when one bird flies, for whatever reason, the 

 rest take alarm and fly also. But where different 

 species of birds are all banded together, it seems very 

 * My very close proximity must be taken into account. 



