A THEORY OF BIRDS' NESTS 



natural phenomena 1 Do they teach us anything of the way 

 in which nature works, and give us any insight into the 

 causes which have brought about the marvellous variety, and 

 beauty, and harmony of living things? I believe we can 

 answer these questions in the affirmative ; and I may mention, 

 as a sufficient proof that these are not isolated facts, that I 

 was first led to see their relation to each other by the study 

 of an analogous though distinct set of phenomena among in- 

 sects, that of protective resemblance and " mimicry." 



On considering this remarkable series of corresponding 

 facts, the first thing we are taught by them seems to be, that 

 there is no incapacity in the female sex among birds to receive 

 the same bright hues and strongly contrasted tints with which 

 their partners are so often decorated, since whenever they are 

 protected and concealed during the period of incubation they 

 are similarly adorned. The fair inference is, that it is chiefly 

 due to the absence of protection or concealment during this 

 important epoch, that gay and conspicuous tints are withheld 

 or left undeveloped. The mode in which this has been effected 

 is very intelligible, if we admit the action of natural and 

 sexual selection. It would appear from the numerous cases 

 in which both sexes are adorned with equally brilliant colours 

 (while both sexes are rarely armed with equally developed 

 offensive and defensive weapons when not required for indi- 

 vidual safety), that the normal action of " sexual selection " or 

 of other unknown causes, is to develop colour and beauty in 

 both sexes, by the preservation and multiplication of all 

 varieties of colour in either sex which are pleasing to the 

 other. Several very close observers of the habits of animals 

 have assured me that male birds and quadrupeds do often 

 take very strong likes and dislikes to individual females, and 

 we can hardly believe that the one sex (the female) can have 

 a general taste for colour while the other has no such taste. 

 However this may be, the fact remains, that in a vast number 

 of cases the female acquires as brilliant and as varied colours 

 as the male, and therefore most probably acquires them in the 

 same way as the male does that is, either because the 

 colour is useful to it, or is correlated with some useful varia- 

 tion, or is pleasing to the other sex. The only remaining 

 supposition is that it is transmitted from the other sex, with- 

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