behaviour in relation to the territory can be studied more conveniently where a number of individuals of the same species have established themselves in proximity to one another. Such species as the Chiffchaff, Willow- Warbler, 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 suitable subject for an investigation of this kind; for since it is restricted by its habits to localities wherein the common reed (Arundo phragmites) 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.
