India, vol. iii. pp. 618, 621.) In a widely different group of birds,
namely Humming-birds, the males alone of certain kinds have either the
shafts of their primary wing-feathers broadly dilated, or the webs
abruptly excised towards the extremity. The male, for instance, of
Selasphorus platycercus, when adult, has the first primary wing-feather
(Fig. 44), thus excised. Whilst flying from flower to flower he makes
a shrill, almost whistling noise (56. Gould, Introduction to the
Trochilidae, 1861, p. 49. Salvin, Proceedings, Zoological Society,
1867, p. 160.); but it did not appear to Mr. Salvin that the noise was
intentionally made.
[Fig. 45. Secondary wing-feathers of Pipra deliciosa (from Mr. Sclater,
in Proc. Zool. Soc. 1860). The three upper feathers, a, b, c, from
the male; the three lower corresponding feathers, d, e, f, from the
female. a and d, fifth secondary wing-feather of male and female, upper
surface. b and e, sixth secondary, upper surface. c and f, seventh
secondary, lower surface.]
Lastly, in several species of a sub-genus of Pipra or Manakin, the
males, as described by Mr. Sclater, have their SECONDARY wing-feathers
modified in a still more remarkable manner. In the brilliantly-coloured
P. deliciosa the first three secondaries are thick-stemmed and curved
towards the body; in the fourth and fifth (Fig. 45, a) the change is
greater; and in the sixth and seventh (b, c) the shaft is thickened to
an extraordinary degree, forming a solid horny lump. The barbs also
are greatly changed in shape, in comparison with the corresponding
feathers (d, e, f) in the female. Even the bones of the wing, which
support these singular feathers in the male, are said by Mr. Fraser to
be much thickened. These little birds make an extraordinary noise, the
first sharp note being not unlike the crack of a whip. (57. Sclater,
in Proceedings, Zoological Society, 1860, p. 90, and in Ibis, vol.
iv. 1862, p. 175. Also Salvin, in Ibis, 1860, p. 37.)
The diversity of the sounds, both vocal and instrumental, made by the
males of many birds during the breeding-season, and the diversity of
the means for producing such sounds, are highly remarkable. We thus
gain a high idea of their importance for sexual purposes, and are
reminded of the conclusion arrived at as to insects. It is not
difficult to imagine the steps by which the notes of a bird, primarily
used as a mere call or for some other purpose, might have been improved
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