BRITISH WARBLERS 



away and she must be the stimulus unless the emotion is spon- 

 taneous, arising, Ave know not how, from the sexual condition 

 of the male. In either case the feelings which prompt the 

 bird to action can scarcely be those of displeasure, and we have 

 indisputable evidence that the movement of the wings can be 

 associated with a pleasurable emotion, since the female nutters 

 them at a moment when her desires are perfectly clear. So 

 that here again there appears to be a similarity of response 

 under the influence of a dissimilar emotion. The presence of 

 another male or of an individual of another species may cause 

 a general relaxing of the feathers and a spreading of wings on 

 the part of the male, and this attitude sometimes appears to 

 be the prelude to an attack, but the emotion, whatever it may 

 be, disappears upon the retreat of the intruder. Why should 

 the presence of an individual of another species influence the 

 behaviour of the male ? We shall find this question difficult 

 to answer. The passing of a stranger through his territory 

 may possibly evoke different emotions at different times and 

 yet produce similar motor reactions. This is just the difficulty. 

 There is the playful tendency, so common in the higher 

 animals, which might be readily awakened by a harmless 

 intruder of another species. On the other hand, the question of 

 territory may here also dominate the situation and the intrusion 

 may be genuinely resented. Who can say with any degree of 

 certainty in which direction we are to look for the real factor ? 

 And with this first step undetermined, what useful purpose can 

 be served by attempting to locate the true emotion ? Attention 

 may nevertheless be called to this one point ; the attitudes 

 affected by the male upon the intrusion of an individual of 

 another species are similar in all respects to those caused by 

 resentment at the approach of another male of the same 

 species. 



In one instance that came under my notice a male Sedge 

 Warbler took possession of the same territory as a Marsh 

 Warbler ; and, further, made use of the same willow tree as 

 his headquarters. This tree was situated only a few yards 



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