270 THE PRINCIPLES OF Part II. 



be polygamous. With the Grallatores, extremely few 

 species differ sexually, but the ruff" (Machetes pugnax) 

 affords a strong exception, and this species is believed 

 by Montagu to be a polygamist. Hence it appears 

 that with birds there often exists a close relation 

 between polygamy and the development of strongly- 

 marked sexual differences. On asking Mr. Bartlett, at 

 the Zoological Gardens, who has had such large ex- 

 perience with birds, whether the male tragopan (one of 

 the Gallinacere) was polygamous, I was struck by his 

 answering, " I do not know, but should think so from 

 " his splendid colours." 



It deserves notice that the instinct of pairing with a 

 single female is easily lost under domestication. The 

 wild-duck is strictly monogamous, the domestic-duck 

 hiprhlv polv^amous. The Rev. W. D. Fox informs me 

 that with some half-tamed wild-ducks, kept on a large 

 pond in his neighbourhood, so many mallards were shot 

 bv the gamekeeper that only one was left for every 

 seven or eight females ; yet unusually large broods 

 were reared. The guinea-fowl is strictly monogamous ; 

 but Mr. Fox finds that his birds succeed best when he 

 keeps one cock to two or three hens. 9 Canary-birds 

 pair in a state of nature, but the breeders in England 

 successfully put one male to four or five females ; never- 

 theless the first female, as Mr. Fox has been assured, 

 is alone treated as the wife, she and her young ones 

 being fed by him ; the others are treated as concubines. 

 I have noticed these cases, as it renders it in some 

 degree probable that monogamous species, in a state of 

 nature, might readily become either temporarily or per- 

 manently polygamous. 



9 The Rev. E. S. Dixon, however, speaks positively (' Ornamental 

 Poultry,' 1S48, p. 76) about the eggs of the guinea-fowl being infertile 

 when more than one female is kept with the same male. 



