BRITISH WARBLERS
hesitation which is assumed to be an essential prelude to conjugation. Elsewhere I have suggested that such a use of the term is open to criticism. And since it is possible that from the moment a sexually mature female enters the territory of a single male the question of reproduction is decided, providing always that she is not challenged and defeated by a rival of the same sex, I have referred, in the later parts of this work, to the whole of the period commencing with the arrival of the female and ending with the laying of the normal number of eggs as that of sexual activity. During this period the emotional manifestation, which is unequalled at any other period in volume though sometimes not in intensity, may perhaps be said to reach its climax during the actual discharge of the sexual function, and the manifold and peculiar antics and attitudes which we witness must be regarded as part of a whole—that is to say, as part of the sexual instinct. The problem, then, which requires a solution is the exact position that these activities occupy in the whole sexual process; but so long as we are ignorant of so many simple facts in the lives of so many species, it is scarcely likely that a satisfactory solution will be reached.
If it were possible to induce one pair of each of our more common species of warblers to rehearse its life-history before an onlooker previously unacquainted with their habits, one feature which would perhaps command a large share of his attention would be the fact that each species has its own degree of response, which is constant even at the different emotional periods. He would notice that this pair was persistently sluggish in behaviour, while that pair was scarcely able to restrain its excitement on the slightest provocation. In all likelihood he would thereupon call to mind all he knew of human emotion, and possibly satisfy himself that an analogy was to be found in the behaviour of the different races of man. And so long as the analogy were limited to this particular feature, it would approximate in some measure to the actual facts. We enter in the latter part of April some wood in-
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