BRITISH WARBLERS
erecting his feathers and singing continuously. When one female temporarily disappears, he immediately commences to pay attention to the remaining one, precipitating himself towards her after his manner, and discontinuing only on the return of the other female. A struggle of this kind sometimes results in the disappearance of both the females, the one having apparently driven the other away, the male being thus left alone unmated for perhaps another ten days.
The period between the time when a female arrives in a territory of a given male, and the time when the first egg is laid is a varying one. Though commonly referred to as the period of courtship, it is probably one of fertilisation and development only. Before finally deciding one way or the other, it is above all things necessary to know when the first act of coition takes place, whether a single act suffices for the fertilisation of all the eggs, or each egg requires separate fertilisation. Now of all this we have little enough knowledge even of our domestic creatures. How, then, can it be expected that we should obtain sufficient evidence to be of value in the case of wild ones? With the larger species it might, by very close study, be possible to obtain this, but as far as the smaller birds, ever moving and flitting from bush to bush, are concerned, it will always remain a difficult matter to acquire the necessary knowledge. Yet without this knowledge a complete understanding of the numerous diverse activities occurring at this period is impossible. But we can still attempt to understand them in part, and in order to do this we must utilise the only other means at our disposal, namely, deduction from the general behaviour of both sexes. And it is just because, speaking generally, there is a gradual diminution of excitement, which would naturally be the result of fertilisation and not an increase, or at any rate a continuity of the excitement, which would result from a prolonged courtship, that I am led to believe that the period is one of fertilisation and not of courtship. By copying from my notes a brief description of the behaviour of a pair in the morning
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