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, sono 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, larve, and various small fruits. It is a 
somewhat late breeder, the eggs being laid during May 
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