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Descent of Man [ 1871]

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Author Topic: Descent of Man [ 1871]  (Read 2928 times)
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« Reply #135 on: February 10, 2009, 01:12:04 pm »

Chapter XIV - Birds- Continued

  WHEN the sexes differ in beauty or in the power of singing, or in
producing what I have called instrumental music, it is almost
invariably the male who surpasses the female. These qualities, as we
have just seen, are evidently of high importance to the male. When
they are gained for only a part of the year it is always before the
breeding-season. It is the male alone who elaborately displays his
varied attractions, and often performs strange antics on the ground or
in the air, in the presence of the female. Each male drives away, or
if he can, kills his rivals. Hence we may conclude that it is the
object of the male to induce the female to pair with him, and for this
purpose he tries to excite or charm her in various ways; and this is
the opinion of all those who have carefully studied the habits of
living birds. But there remains a question which has an all
important bearing on sexual selection, namely, does every male of
the same species excite and attract the female equally? Or does she
exert a choice, and prefer certain males? This latter question can
be answered in the affirmative by much direct and indirect evidence.
It is far more difficult to decide what qualities determine the choice
of the females; but here again we have some direct and indirect
evidence that it is to a large extent the external attractions of
the male; though no doubt his vigour, courage, and other mental
qualities come into play. We will begin with the indirect evidence.
  Length of Courtship.- The lengthened period during which both
sexes of certain birds meet day after day at an appointed place
probably depends partly on the courtship being a prolonged affair, and
partly on reiteration in the act of pairing. Thus in Germany and
Scandinavia the balzen or leks of the black-cocks last from the middle
of March, all through April into May. As many as forty or fifty, or
even more birds congregate at the leks; and the same place is often
frequented during successive years. The lek of the capercailzie
lasts from the end of March to the middle or even end of May. In North
America "the partridge dances" of the Tetrao phasianellus "last for
a month or more." Other kinds of grouse, both in North America and
Eastern Siberia,* follow nearly the same habits. The fowlers
discover the hillocks where the ruffs congregate by the grass being
trampled bare, and this shews that the same spot is long frequented.
The Indians of Guiana are well acquainted with the cleared arenas,
where they expect to find the beautiful cocks of the rock; and the
natives of New Guinea know the trees where from ten to twenty male
birds of paradise in full plumage congregate. In this latter case it
is not expressly stated that the females meet on the same trees, but
the hunters, if not specially asked, would probably not mention
their presence, as their skins are valueless. Small parties of an
African weaver (Ploceus) congregate, during the breeding-season, and
perform for hours their graceful evolutions. Large numbers of the
solitary snipe (Scolopax major) assemble during dusk in a morass;
and the same place is frequented for the same purpose during
successive years; here they may be seen running about "like so many
rats," puffing out their feathers, flapping their wings, and
uttering the strangest cries.*(2)

  * Nordman describes (Bull. Soc. Imp. des Nat. Moscou, 1861, tom.
xxxiv., p. 264) the balzen of Tetrao urogalloides in Amur Land. He
estimated the number of birds assembled at above a hundred, not
counting the females, which lie hid in the surrounding bushes. The
noises uttered differ from those of T. urogallus.
  *(2) With respect to the assemblages of the above-named grouse,
see Brehm, Thierleben, B. iv., s. 350; also L. Lloyd, Game Birds of
Sweden, 1867, pp. 19, 78. Richardson, Fauna Bor. Americana: Birds,
p. 362. References in regard to the assemblages of other birds have
already been given. On Paradisea, see Wallace, in Annals and Mag. of
Nat. Hist., vol. xx., 1857, p. 412. On the snipe, Lloyd, ibid., p.

  Some of the above birds,- the black-****, capercailzie,
pheasant-grouse, ruff, solitary snipe, and perhaps others,- are, as is
believed, polygamists. With such birds it might have been thought that
the stronger males would simply have driven away the weaker, and
then at once have taken possession of as many females as possible; but
if it be indispensable for the male to excite or please the female, we
can understand the length of the courtship and the congregation of
so many individuals of both sexes at the same spot. Certain strictly
monogamous species likewise hold nuptial assemblages; this seems to be
the case in Scandinavia with one of the ptarmigans, and their leks
last from the middle of March to the middle of May. In Australia the
lyre-bird (Menura superba) forms "small round hillocks," and the M.
Alberti scratches for itself shallow holes, or, as they are called
by the natives, corroborying places, where it is believed both sexes
assemble. The meetings of the M. superba are sometimes very large; and
an account has lately been published* by a traveller, who heard in a
valley beneath him, thickly covered with scrub, "a din which
completely astonished" him; on crawling onwards he beheld, to his
amazement, about one hundred and fifty of the magnificent
lyre-cocks, "ranged in order of battle, and fighting with
indescribable fury." The bowers of the bower-birds are the resort of
both sexes during the breeding-season; and "here the males meet and
contend with each other for the favours of the female, and here the
latter assemble and coquet with the males." With two of the genera,
the same bower is resorted to during many years.*(2)

  * Quoted by Mr. T. W. Wood, in The Student, April, 1870, p. 125.
  *(2) Gould, Handbook of the Birds of Australia, vol. i., pp. 300,
308, 448, 451. On the ptarmigan, above alluded to, see Lloyd, ibid.,
p. 129.

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