248 THE DESCENT OP MAN. 



Among birds, many species, the sexes of which differ 

 greatly from each other, are certainly monogamous. In 

 Great Britain we see well-marked sexual differences, for 

 instance, in the wild duck which pairs with a single female, 

 the common blackbird, and the bullfinch which is said to 

 pair for life. I am informed by Mr. Wallace that the like 

 is true of the Chatterers or Cotingid^e of South America, 

 and of many other birds. In several groups I have not. 

 been able to discover whether the species are polygamous or 

 monogamous. Lesson says that birds of paradise, so 

 remarkable for their sexual differences, are polygamous, but 

 Mr. Wallace doubts whether he had sufficient evidence. 

 Mr. Salvin tells me he has been led to believe that hum- 

 ming - birds are polygamous. The male widow - bird, 

 remarkable for his caudal plumes, certainly seems to be a 

 polygamist.* I have been assured by Mr. Jenner Weir and 

 by others that it is somewhat common for three starlings to 

 frequent the same nest; but whether this is a case of 

 polygamy or polyandry has not been ascertained. 



The Gallinacese exhibit almost as strongly marked sexual 

 differences as birds of paradise or humming-birds, and 

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

 others being strictly monogamous. What a contrast is pre- 

 sented between the sexes of the polygamous peacock or 

 pheasant, and the monogamous guinea-fowl or partridge! 

 Many similar 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 monagamous 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 Grallatores extremely few species differ sexually, but 

 the ruff' {Machetes piignax) 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 

 relation between polygamy and the development of strongly- 



*"The Ibis," vol. iii, 1861, p. 133, on the Progne Widow-bird. 

 See also on tlie Vidua axillaHs, ibid., vol. ii, 1860, p. 211. On the 

 polygamy of tlie Capercailzie and (jreat Bustard, see Ij. Lloyd, 

 "Game Birds of Sweden," 1867, pp. 19, 183. Montagu and Selby 

 speak of the Black Grouse as polygamous and of the Red Grouse as 

 monogamous. 



