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 stretch- 

 ing 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 through- 

 out 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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