The Descent of Man

known to make a humming noise whilst courting
the female. (55. Jerdon, 'Birds of 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 wingfeather
(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