290 THE DESCENT OF MAN 



of the species are, as is well known, polygamous; others 

 being strictly monogamous. What a contrast is presented 

 between the sexes of the polygamous peacock or pheasant 

 and the monogamous guinea-fowl or partridge! Many simi- 

 lar cases could be given, as in the grouse tribe, in which the 

 males of the polygamous capercailzie and black-cock differ 

 greatly from the females; while the sexes of the monoga- 

 mous red grouse and ptarmigan differ very little. In the 

 Cursores, except among the bustards, few species offer 

 strongly marked sexual differences, and the great bustard 

 {Otis tarda) is said to be polygamous. With the Gralla- 

 tores, extremely few species differ sexually, but the ruff 

 {Machetes pugnax) affords a marked exception, and this 

 species is believed by Montagu to be a polygamist. Hence 

 it appears that among birds there often exists a close rela- 

 tion between polygamy and the development of strongly 

 marked sexual differences. I asked Mr. Bartlett of the 

 Zoological Gardens, who has had very large experience 

 with birds, whether the male tragopan (one of the Gal- 

 linacese) was -polygamous, and I was struck by his an- 

 swering, "I do not know, but should think so from his 

 splendid colors." 



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 highly polyga- 

 mous. The Rev. W. D. Fox informs me that out of some 

 half-tamed wild-ducks, on a large pond in his neighborhood, 

 so many mallards were shot by the gamekeeper that only 

 one was left for every seven or eight females; yet unusually 

 large broods were reared. The guinea-fowl is strictly mo- 

 nogamous; but Mr. Fox finds that his birds succeed best 

 when he keeps one cock to two or three hens. Oanary- 

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

 successfully put one male to four or five females. I have 

 noticed these cases, as rendering it probable that wild mo-, 

 nogamous species might readily become either temporarily 

 or permanently polygamous. 



