REED WARBLER 



that, in the case of many species, they are so seldom in 

 evidence. But this we can understand if we remember that 

 such birds would be restless wanderers, not resident in any 

 one particular locality, but continually being urged to move 

 from place to place by their sexual instinct ; and, if at 

 any time they should happen to be in or near a territory 

 already occupied, they would be, no doubt, desirous of 

 concealing their presence. This fact of the unpaired birds 

 being so seldom in evidence, while at the same time so 

 numerous, is one of some importance. It emphasises the 

 close connection that must exist between territory and repro- 

 duction, for if there is no law of territory how can their 

 behaviour be explained ? Why should not the unpaired males 

 instead of wandering about, apparently wishing to remain 

 unobserved, be content to stay in one particular locality and 

 make their presence known by song, as the majority of the 

 males do who secure mates ? 



Many species have extended their breeding range in recent 

 years and are even now extending it. It may be said that 

 this extension is not real, but only apparent, owing to the 

 greater interest taken in Nature by a consequently greater 

 number of competent observers, so that whereas formerly a 

 species, although present, remained unobserved, at the present 

 time it is immediately detected. There is no doubt some 

 truth in this, but at the same time there is strong evidence 

 to show that in many cases the breeding range has unques- 

 tionably been extended. If the extension were limited to 

 those species only whose numerical strength was exceptionally 

 great, it would not, perhaps, be quite so surprising. But this 

 is not the case ; even those that are not numerous are slowly 

 but steadily increasing their range. There is no direct neces- 

 sity, so far as reproduction is concerned, for a bird to desert 

 the particular neighbourhood in which it was reared ; in fact, 

 there would seem to be an advantage in its not doing so, since 

 there would be a greater likelihood of securing a mate in a 

 district already inhabited by the species ; neither is there any 



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