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 fæces 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 larvæ 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 hesitation swallowed it. Proceeding then as usual to clean the nest he picked up one of the leaves, and to my astonishment 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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