Territorialism and *' Sexual Selection** 55 



A familiar and easily observed territorial bird is the robin. Cape 

 or British. He is a strict territorial, apparently, all the year round, 

 yet though I have often seen him dash at an intruder I have never 

 seen the introduer resist so that a set fight ensued, and on the 

 whole what a peaceable life Jan Frederic lives. He sings his 

 procl amatory song night and morning, curses the cat from bush to 

 bush when there is a family, but I have observed little if any in- 

 terruption of business by interlopers. The appearance of terri- 

 torial birds proclaims the same thing, neither Jan Frederic or your 

 smart coloured sunbird are battered or dishevelled in the process 

 of keeping their territories intact. As a matter of fact they 

 probably have not a feather awry. If then we may assume, as 

 both observation and common sense seem to tell us, that nature 

 has no use for fighting, we can understand the adoption of vari- 

 ous devices for reconciling the necessity of territorialism with as 

 little destructive fighting as possible. The song of birds has been 

 recognised as such a device, then why not colour? On this view 

 tiie red on the robin's breast is a warning colour which catching 

 the eye of a trespasser saves further trouble by informing him 

 that the territory is occupied (B). 



All the difficulties attending the theory of sexual selection 

 need not be recapitulated here, but one of them concerns us i.e. 

 it is not the beauty or strength of the male which is the 

 deciding factor at the critical moment but simple propinquity. 

 In other words in Nature when internal conditions cause the 

 female to desire the male the first male to seize the opportunity 

 is accepted, and this holds good even in the case of birds which 

 are paired. 



It is obvious therefore that apart from the question of food 

 supply the bird whether polygamous or monogamous which keeps 

 its territorial well clear of hangers on will leave most of its own 

 progeny. In other words the purposes fulfilled by territorialism 

 are one or both of the following, ( 1 ) the conservation of a food 

 supply, (2) the jealous reservation of the female partner or 

 partners. If it is expedient that this should be done with as 

 little interruption of life's business by fighting as possible, then the 

 development of brilliant colours in male territorial birds can be 



