88 DISPOSITION TO DEFEND THE TERRITORY 



the struggles between paired birds, and which 

 we grant is purposeless, would be more than 

 balanced by the added security." This is a 

 possible explanation and requires consideration. 

 It cannot account for all the diverse ways in 

 which the sexes are mixed up in the fighting 

 it cannot, for instance, explain the fact that an 

 unpaired male will attack either sex of an 

 adjoining pair indiscriminately but nevertheless 

 it appears at first sight to be a reasonable 

 explanation of some of them. We must 

 remember, however, that fighting continues 

 throughout the whole period of reproduction. 

 Even after the discharge of the sexual function 

 has ceased, and the female is engaged in incuba- 

 tion or in tending her young, the male is still 

 intolerant of intruders ; and it is difficult to 

 believe that, at so late a stage in the process, a 

 female could be any attraction sexually to an 

 unpaired male. But apart from any theoretical 

 objection, there remains the fact namely that 

 there is no evidence that a male, after having 

 once paired, is liable to be robbed of its mate. 

 And in support of this fact I have only to state 

 that I have met with no single instance of 

 failure to obtain and hold a mate when once a 

 territory had been secured. Bearing in mind 

 then that both sexes participate in the fighting, 

 and that individuals of the opposite sex fre- 

 quently attack one another ; that all such 

 conflicts are characterised by persistent effort, 

 and that they are not limited to just the 

 particular period when the sexual instinct is 



