BRITISH WARBLERS
fluttering her wings rapidly, raising her tail, and continuing thus for some seconds, an attitude indicative in many species of a desire for coition. Her sexual emotion is expressed in another hut more peculiar form. This is an alternate stretching of the wings, and although the degree of expansion is only slight yet the movement is sufficiently conspicuous, and is slowly executed. I have seen her when under the influence of excitement behave still differently, but the direct stimulus was not clear, and therefore it is impossible even to suggest what the emotion may have been. That she was labouring under the influence of some considerable emotion was evident, for she spread her tail and waved her wings slightly, an attitude similar to that affected by the male. Now all these various ways by which the sexual emotion of both sexes is betrayed are not confined to one day, or a few days, after the arrival of a female; they are not, that is to say, antecedent only to conjugation, but occur throughout the whole of the period of sexual activity. At the risk of repeating myself I will again define what is meant by this period. It comprises the whole of that time between the arrival of a female in a given territory and the laying of the full complement of eggs. Where a second brood is produced, either from natural causes or as the result of the first brood being destroyed, there is a recurrence of this activity, and, consequently, of emotional behaviour. But this need not be considered here, since it is a repetition only of that which occurs during the first period. The activities referred to are in evidence throughout the whole of the period, but their intensity becomes gradually less and less marked. The song is neither uttered so frequently nor so violently, the periods of silence become longer, the flying at the female by the male occurs less frequently, and ultimately the excitement in a great measure disappears. The gradual diminution in the song during this period is interesting. I recollect one instance in which it almost ceased upon the arrival of a female, and this case is not without a parallel
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