EFFECT OF ISOLATION 273 



scarcity, now set forth alone and settle first here 

 and then there in search of isolation. Lapwings 

 settle in the water meadows, and, finding them- 

 selves forestalled, pass on in search of other 

 ground ; Blackbirds arrive in a coppice or in a 

 hedgerow and, meeting with opposition, dis- 

 appear ; and the Curlew, wandering with no 

 fixed abode but ai)parently with a fixity of 

 purpose, searches out the moorland where it can 

 find the particular environmental conditions to 

 which its inherited nature will respond. In 

 fact, wherever we choose to look, we can 

 observe in a general way the gradual appropria- 

 tion of breeding ground ; and if we fix our 

 attention upon particular males, we can watch 

 the method by which success or failure is 

 achieved. 



On more than one occasion I have watched 

 the efforts of Reed-Buntings to appropriate 

 territories in a marsh that was already inhabited. 

 Sometimes their efforts met wdth success, at 

 other times with failure. In the former case, 

 the males, whose ground was intruded upon, were 

 severally forced to yield part of their holding 

 and were thus left in possession of a smaller 

 area. The success of the intruder seemed to 

 depend upon persistent determination, rather 

 than upon superior skill in battle. Recently I 

 had an opportunity of observing the intrusion of 

 a male Willow- Warbler upon ground already 

 occupied. By persistent effort it succeeded in 

 appropriating one half of the territory of its 

 rival. The intruder occupied some trees on the 



