BKITISH WARBLERS 



down to her, and sometimes when very close warbles so 

 quietly that the sound is scarcely audible a few paces away- 

 During these scenes she may flap her wings whilst perched 

 upon a branch, but more usually betrays her emotion 

 by restless behaviour and by uttering various call notes. 

 The presence of a third male evokes much excitement, the 

 owner of the territory spreading and flirting his tail and even 

 flying at the intruder. All this behaviour is clearly but 

 a repetition of that which occurred earlier in the season, 

 and my sole reason for repeating so much of what has 

 already been described is to call attention to the lateness of 

 the date, which requires some explanation. 



An interesting feature of the period of sexual activity is the 

 attitude adopted by the bird towards other species, more especi- 

 ally towards the Blackcap, to which it is closely related. It is 

 the male who more frequently betrays emotion in the presence 

 of a member of another species. Much excitement is caused 

 by the intrusion of a Blackcap, and, in a lesser degree, of 

 a Whitethroat or a pair of Whitethroats, in his territory, and 

 the scenes which ensue remind one forcibly of those which 

 result from the intrusion of a neighbouring male of his own 

 species. We listen to a similarly violent use of the vocal 

 powers into which is infused much feeling tone ; we see 

 similar pursuits taking place, culminating in a flying together 

 with snapping of bills, and observe similar excitement reflexes. 

 What is the biological significance of such behaviour ? If it 

 has no meaning, but is only a manifestation of surplus energy, 

 then it must clearly be included in the category of "play." 

 But in observing the birds under these peculiar circumstances, 

 one is impressed with the persistent striving towards some 

 end which is the accompaniment of such behaviour, and we 

 cannot regard as meaningless behaviour which is so frequent 

 in occurrence, so suffused with feeling tone, and so productive 

 of motor reactions which are customarily associated with 

 feelings of displeasure. What then can the meaning be ? 

 Surely the fact that it is a closely related form that is the 



12 



