CHAPTER VII 



THE SEXUAL SELECTION THEORY AS APPLIED TO BIRDS 



Where the R61e of the Sexes is reversed — Polygamy and how it is 

 brought about — Coloration and Courtship — Instinctive Actions 

 — The Importance of Landed Possessions — ^The Meaning of 

 " Display " — The Springs of " Behaviour " — A New Light on 

 the Wild-duck— The " Display " of the Great-crested Grebe- 

 Some Neglected Factors. 



The significance of the varied behaviour of birds — more 

 especially of the males — during the period of reproductive 

 activity must now be more minutely analysed. But 

 before this analysis can be profitably begun, it will be 

 necessary to recall the fact that there are several cases 

 known wherein the role of the sexes is largely reversed. 

 Herein the females do the " courting," and fight one 

 another as rivals for the males ; while the males perform 

 the duties of incubation and brooding, and feeding the 

 young. This is really very remarkable, and demands more 

 attention than it has yet received. 



What factors have brought about this curious reversal ? 

 In any search for an explanation it must be borne in 

 mind that in all such cases polyandry is the rule, and 

 in all such cases the female is larger and more vividly 

 coloured than the male. Here, then, we have exactly 

 the opposite to what obtains in cases of polygamy. What 



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