THE FINCHES 103 



should the females be brighter, instead of duller, than the males 

 since they more need protection but the very males themselves are 

 hardly bright enough to satisfy them; the parrot tribe, in which 

 neither of these drawbacks obtain, and, of these, the macaws, more 

 especially the scarlet one, say, Ara macao for choice would reward 

 their ingenuity better. 



The next-favoured hypothesis is that of superior vitality in the 

 male, leading to the acquisition by him alone of colour, frills, lappets, 

 etc., at that period especially when vital energy is most required in 

 the cock bird, whilst the hen, who needs but little for egg-laying, nest- 

 building, and care of the young, remains unaffected in youth, that 

 is to say. In age, having lost the capacity for these things, and 

 become more vigorous in consequence, she may sometimes (as noticed 

 by Darwin) assume the attributes of the male to a minor degree- 

 striking collateral testimony to the truth of the main proposition ! 



Accepted frankly, this theory is incidentally useful, as giving us 

 a sure insight into comparative bird psychology and temperament, 

 for since, according to it, the more vigorous the males of any species 

 are, the brighter they glow, we see at once that the cock bullfinch, 

 for instance, whatever the hen may be, is a much brisker bird, not 

 only than the sparrow, but even than the sparrow-hawk and others 

 of the Accipitres, or than the swift, swallow, martin, etc., which we 

 should never have found out had we been forced to rely on our 

 own unaided observation. If, indeed, we allow ourselves to be 

 guided by this, as well as by common knowledge, it becomes 

 apparent that the world is full of extremely vigorous birds that are 

 dull, and much less vigorous ones that are brightly coloured ; but 

 these we are at liberty to account for as exceptions to a rule 

 which, in accordance with a well-known axiom, they thus help to 

 prove. 



But if still unsatisfied, we are then driven back upon the generally 

 unpopular doctrine of sexual selection, which, though it has every 

 possible evidence of fact in its favour even to that of the process 



