BRITISH WARBLERS 
parents, but they respond in accordance with their hunger, 
and if, when one of the parents settles upon the side of 
the nest, there is no response, that parent at once commences 
to brood. I remember once seeing a male, while searching 
for food not far from my hiding-place, suddenly spread out 
his wings and commence to run about in what might almost 
be interpreted as a threatening manner. Such behaviour 
is not uncommon on the part of the female when a nest 
containing young is approached; she will then proceed to 
flutter off and move away along the ground, waving her 
wings and spreading her tail, or she will perform in the 
same way amongst the trees, and whilst hopping from branch 
to branch will spread her tail and wave her wings slowly 
in a similar manner to that observed during the period of 
sexual activity; she will not, however, always act thus, 
but for no apparent reason will perform differently at even 
very short intervals. 
As in the case of many other species, the feces ejected by 
the young are enclosed in a membraneous sac, and by this 
provision of Nature the parents are enabled to carry it in their 
bills, and either remove it some distance from the nest, or else 
swallow it themselves. 
While cutting away vegetation surrounding a particular 
nest, so as to obtain a better view of the proceedings, 
some small leaves of the ground ivy (Nepeta glechoma) 
dropped by mistake, and unknown to me, into the nest itself. 
Soon after I had returned to my hiding-place the male 
appeared carrying some larve in his bill, and settling upon 
the side of the nest placed the food into a young one’s throat ; 
but immediately took it out again, and after some hesita- 
tion swallowed it. Proceeding then as usual to clean the 
nest he picked up one of the leaves, and to my astonish- 
ment swallowed it also. This led to my making further 
experiments, not only with this particular pair of birds but 
with others also. I placed leaves of various sizes, and from 
different plants, into the nest; and the result of the experi- 
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