THE LONELIER HOURS 



167 



hour, one can easily be mistaken for the other. The grass- 

 hopper-warbler's song — for it takes the place of a more 

 musical ditty — possesses nearly as conspicuously as the 

 nightjar's the delicate change of pitch which averts mono- 

 tony and adds a characteristic attraction. In the case of the 

 nightjar the change is said to take place when the bird ceases 



GRASSHOPPER-WARBLER 



to draw in breath and begins to expel it ; but owing to its 

 habits of concealment the grasshopper-warbler is one of the 

 most difficult of all birds to observe, and there is no evidence 

 of the same cause in its case, though it is at least probable. 

 The corncrake's note in the June mowing grass constantly 

 varies in intensity, but has no change of pitch ; and the 

 alternating softness and loudness of its cry is simply due 

 to its turning its head in different directions while it calls. 

 In early May, when the grass is still short, it can sometimes 



