232 WARFARE BETWEEN DIFFERENT SPECIES 



So much, then, for the seasonal change of 

 relationship ; let us now turn to particular cases 

 and attempt to trace the condition which 

 accompanies such change. 



Many migrants in the spring seem to follow 

 the course of the Severn during their journey 

 northwards through Worcestershire ; and where 

 the river bends to the north-west at Lincombe 

 Lock, there they leave it, or, rather, continue 

 in a north-easterly direction which takes them 

 across the southern end of Hartlebury Common. 

 As I have already mentioned, this Common is 

 overgrown with gorse, heather, and ling, and 

 scattered here and there are a number of dwarf 

 oak-trees and small elder-bushes. The situation 

 is therefore an ideal one for the smaller migrants 

 to rest for a brief time, and, from the point of 

 view of the observer, very suitable because it is 

 open and the movements of the birds can be 

 traced for some distance. Turtle Doves pass 

 over at a great height, or skim across a few 

 feet above the gorse ; Redstarts settle for a 

 few minutes and then disappear ; Tree-Pipits, 

 Whinchats, and Willow- Warblers pass from 

 tree to tree or flit from bush to bush — and all 

 in a north-easterly direction. They do not 

 sing, they are restless, and, judging by their 

 behaviour, they are anxious to conceal their 

 presence, not to make it known. Yet we know 

 that when they reach their destination, as 

 presently they will, all this will change ; that 

 each of them will employ every means at its 

 disposal to make itself conspicuous ; and that 



