ISOLATION OF THE MALE 61 



behaviour in relation to the territory can be 

 studied more conveniently where a nunaber of 

 individuals of the same species have established 

 themselves in proximity to one another. Such 

 species as the ChifFchaff, Willow- AVarbler, or 

 Wood- Warbler are often sufficiently common to 

 allow of three or more of their respective males 

 being kept in view at the same time ; and the 

 disposition to occupy a definite position can be 

 readily observed. The Reed- Warbler is a suit- 

 able subject for an investigation of this kind ; 

 for since it is restricted by its Iiabits to localities 

 wherein the common reed {Arundo phi^agmites) 

 grows in abundance, and since such localities 

 are none too plentiful and often limited in 

 extent, the area occupied by each individual is 

 necessarily small — if it were not so the species 

 would become extinct. Hence it is a simple 

 matter to study the routine of the different 

 individuals and to mark the extent of their 

 wanderings. 



In this way the males of all the Warblers 

 that breed commonly in Great Britain establish 

 themselves, each one in its respective station at 

 the respective breeding ground ; so, too, do 

 those of many other migrants — for example, the 

 Whinchat, Wheatear, Tree - Pipit, and Red - 

 backed Shrike. All of these, it is true, are 

 common species — numbers of individuals can 

 often be found in close proximity — and therefore 

 it may be argued that they keep to one position 

 more from pressure of population than from any 

 inherited disposition working towards that end. 



E 



