Forster is said to be surrounded by from twenty to thirty females. In
the North, the male sea-bear of Steller is accompanied by even a
greater number of females. It is an interesting fact, as Dr. Gill
remarks (15. The Eared Seals, American Naturalist, vol. iv. Jan.
1871.), that in the monogamous species, or those living in small
communities, there is little difference in size between the males and
females; in the social species, or rather those of which the males have
harems, the males are vastly larger than the females.
Amongst 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 Cotingidae 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 humming-birds are
polygamous. The male widow-bird, remarkable for his caudal plumes,
certainly seems to be a polygamist. (16. The Ibis, vol. iii. 1861, p.
133, on the Progne Widow-bird. See also on the Vidua axillaris, ibid.
vol. ii. 1860, p. 211. On the polygamy of the Capercailzie and Great
Bustard, see L. Lloyd, Game Birds of Sweden, 1867, pp. 19, and 182.
Montagu and Selby speak of the Black Grouse as polygamous and of the
Red Grouse as monogamous.) 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 Gallinaceae 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 presented 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;
whilst the sexes of the monogamous red grouse and ptarmigan differ very
little. In the Cursores, except amongst the bustards, few species offer
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