The Making of Species 



Weir, who has carefully attended to the habits of 

 birds during many years. There can also be no 

 doubt that the most vigorous, best nourished, 

 and earliest breeders would on an average 

 succeed in rearing the largest number of fine 

 offspring. The males, as we have seen, are 

 generally ready to breed before the females ; the 

 strongest, and with some species the best armed 

 of the males, drive away the weaker ; and the 

 former would then unite with the more vigorous 

 and better-nourished females, because they are 

 the first to breed. Such vigorous pairs would 

 surely rear a larger number of offspring than the 

 retarded females, which would be compelled to 

 unite with the conquered and less powerful males, 

 supposing the sexes to be numerically equal ; and 

 this is all that is wanted to add, in the course 

 of successive generations, to the size, strength, 

 and courage of the males, or to improve their 

 weapons." 



From this competition among the males there 

 arise, firstly, contests between the males for 

 mates ; secondly, the preference of the females 

 for favoured males. 



It is a matter of common knowledge that at 

 the breeding season the males of nearly all, if 

 not all, species are very pugnacious. Two 

 males often engage in desperate fights for one 

 or more females ; the victor drives away his foe 

 and secures the harem. In such contests the 



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