REED WARBLER 



moreover, they would have recovered from the fatigue of their 

 long journey, and would thus be in a better position to 

 struggle when challenged by a later arrival ; Nature's process 

 is therefore a simple one, requiring no recognition on the 

 part of the males of territories as such ; their whole behaviour 

 can be accounted for otherwise — and, what is more important 

 still, without our having recourse to complex principles of 

 explanation. 



A male, however, does not always have to fight for its 

 territory. It happens, and not infrequently, that its rights to 

 ownership are recognised, and only when these rights are 

 disputed, either by a later arrival, or by another male arriving 

 simultaneously, does a struggle ensue. Thus we have the 

 spectacle, as in the case of the Blackcap, of two or three males 

 following one another for a short time after their arrival, 

 finally separating amicably and taking possession of adjacent 

 territories. 



A truer definition of the order of migration would be this : 

 Some males arrive before others, and some females arrive 

 before others, but males arrive before females. The same 

 factor which causes males to arrive before females is possibly 

 the cause of the discrepancy in the time of arrival of the 

 individuals of both sexes. We can of course say of the 

 females, as we can of the males, that the earlier arrivals are 

 probably the more vigorous ; but this does not explain, any 

 more than in the case of the males, why one individual hurries 

 off before another. Moreover, if we accept such an explana- 

 tion, we are at once faced with a difficulty, and a very con- 

 siderable one, namely, that the stronger females and the 

 weaker males will travel in company. And if, for the moment, 

 we assume that territory has no control over reproduction, 

 what incentive would there be for the stronger females to seek 

 the stronger males scattered throughout the different districts, 

 and consequently what could possibly prevent their breeding 

 with the weaker males, thereby frustrating the very result for 

 which we all believe Nature is for ever striving, the mainten- 



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