BRITISH WARBLERS 
are built up and washed away a number of times during 
the same season, and each time the same position on the wall 
is chosen: only in an occasional instance are the young 
successtully reared. ‘These cases are, I think, sufficient to 
make clear my meaning; but no doubt a number of similar 
ones will suggest themselves. 
Their food is principally insects and their larve. I have 
not seen them feeding on berries, although they spend 
considerable time in the autumn hopping about amongst 
the elder bushes (Sambucus nigra) when the fruit is ripe. 
On their arrival in March and during the first part of 
April their principal food is Chirononide. In pursuit of 
these insects they search minutely the under side of the 
leaves of different evergreens, such as holly, ivy, &c., and 
the trunks of the larger trees, upon which these flies fre- 
quently cluster, almost the only species sufficiently numerous, 
during the cold east winds, to afford food. In April also they 
search the bare branches and trunks of the different trees for 
the young stages of Psocide, minute white insects, which 
can only be identified by a very close examination. It is 
insects, probably Ciironomide, that are the cause of their 
searching the grass on lawns, where they hop about hunting 
the ground very quickly. ‘They can sometimes be seen 
clinging to the trunks of apple trees in order to pick off 
the small moth-like flies of the genus Psychoda. In May 
and June they take quantities of the larve of Chimatobia 
brumata and Tortrix viridana. This latter insect, the oak 
leaf roller moth, causes very great destruction in some years 
to the oaks. If you stand under one of these trees some 
warm evening in May you will notice that the foliage is 
everywhere riddled, blighted, and partially destroyed by the 
larve, and that the undergrowth is covered with their 
excrement. Now watch these little Warblers, together with 
Whitethroats, Willow-Warblers and Blackcaps, at work ; 
notice their insatiable appetite and the energy with which 
they seek their food; thus we come to understand the danger 
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