BRITISH WARBLERS 



a vanquished male bears at least the impress of reality — 

 though it must be admitted that the quarrels are often of a 

 transitory nature, mere bickerings, a flying at one another 

 followed by a short pursuit and nothing more ; yet even so, 

 the end for which the birds are striving is probably attained. 

 The life of the Wood Warbler affords ample evidence of racial 

 warfare, and the Willow Warbler, probably because it is 

 plentiful and inhabits a similar environment, is of all others 

 the one with which its interests seem more frequently to clash. 

 To observe these quarrels it is necessary to keep in close 

 touch with some particular male from the day of its arrival, 

 to learn its daily routine, and at the same time to know 

 something of the habits of the surrounding species ; to inter- 

 pret them is impossible without the initial knowledge thus 

 acquired. Again and again this mutual antipathy between 

 these two species can be observed during the short period in 

 which they are slaves to the reproductive instinct, and I hope 

 I shall not be accused of needless repetition if I suggest that 

 these struggles ensure, to the stronger, reproduction and 

 a full measure of success in the rearing of offspring, and are 

 therefore related to a larger scheme of which they are but 

 the expression points. It is difficult enough to determine by 

 direct observation whether a species is increasing or diminish- 

 ing in a particular locality, still more difficult to establish any 

 relation between the success of the one and the failure of the 

 other. 



Upon the arrival of a female, a considerable change mani- 

 fests itself in the behaviour of the male. Previous to her 

 appearance on the scene his daily existence was marked with 

 little excitement apart from the quarrels already referred 

 to, but now that is all changed, the sexual instinct 

 asserts itself, and he becomes for a time the slave of the 

 accompanying emotion. The first indication we have of 

 the near approach of conjugation is one which would scarcely 

 seem to portray an increase of excitement, namely, a decrease 

 in the volume of the song. Instead of exercising his vocal 



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