118 DISPOSITION TO DEFEND THE TERRITORY 



that males are hostile when no female is present 

 and hence we must seek elsewhere for the true 

 explanation. 



Now if the behaviour of a male be closely 

 observed, it will be found that its pugnacious 

 instinct gains or loses susceptibility according to 

 the position which it happens to occupy when 

 its ground is trespassed upon, the impulse to 

 fight is strong ; but when it crosses the boundary 

 it seems to lose all interest in the intruder. 

 Moreover, in some species, the male rejoins 

 the flock at intervals during the early part 

 of the season and for a time leads a double 

 existence, passing backwards and forwards 

 between its territory and the neutral ground. 

 Its behaviour under these circumstances affords 

 some valuable evidence, for the bird displays 

 little if any hostility when accompanying the 

 flock, yet when it returns to the ground over 

 which it exercises dominion, no male can 

 approach without being attacked. The conclu- 

 sion, therefore, seems to be inevitable, namely 

 that the actual occupation of a territory is the 

 condition under which the pugnacious nature of 

 the male is rendered susceptible to appropriate 

 stimulation. 



