THE BIRD-LIFE OF LONDON 



masses of vegetation by the waterside. Here it skulks the 

 summer through, its actions more like those of a mouse than 

 wbird, and only at irregular and quiet intervals appearing 

 a ithin view, when it seems to think it is not observed. 

 The slightest alarm sends it quickly to cover, and then 

 only the vibration of a twig here and there or the trem- 

 bling of the tall grass-stems indicates its creeping, gliding 

 passage through the dense cover. Possibly this Warbler 

 may arrive in the London area about the middle of April, 

 but its appearance is seldom noted until its presence is 

 disclosed by its curious song, which is usually first heard 

 near the end of that month, or in some seasons not before 

 the beginning of May. Its departure also is somewhat 

 a matter of conjecture, but close and persistent observa- 

 tion fixes the date as the end of August or early in Sep- 

 tember. It must be remembered that the bird is then 

 practically silent, so no clue to its movements or presence 

 is afforded by its voice. The chirp of the grasshopper 

 or the squeak of the field-mouse prolonged for as long as 

 several minutes at a time will give a good imitation of 

 the voice of the Grasshopper Warbler. It announces its 

 presence with this persistent, monotonous trill, like no 

 other bird-music in England, which is uttered not only 

 at all hours of the day, but very often during the warm, 

 still summer nights. This curious song appears to be 

 confined to the male, but both sexes utter the usual tec- 

 tec call-note so common with the Warblers in general. 

 At fitful intervals a glimpse of the bird may be obtained, 

 either when driven out of one cover to another or when 

 for a fleeting moment it runs up some taller stem or 

 branch than the rest, and then drops down again. Its 

 flight seems feeble enough, but that its powers of wing 

 are considerable is proved by the long migrations it per- 

 forms twice every year. The food of this Warbler con- 

 sists of insects, larvae, and various small fruits. It is a 

 somewhat late breeder, the eggs being laid during May 

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