n 



78 The Descent of Man. Part II. 



The male alone of one of the Indian bustards (Sypheotides 

 auritus) has its primary wing-feathers greatly acuminated; and 

 the male of an allied species is known to make a humming noise 



whilst courting the female. 55 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 in- 



Fig. 44. Primary wing-feather of a stance, of Selasphorus J'latycerciis, 

 Humming-bird, the Seiasphorus pla- w i, PT1 n A-,*,U line tbp first nrimnrv 

 tycercus (from a sketch by Mr. Sal- Wlien aCUUt, lias me niSI piimaiy 



vin). Upper figure, that of male ; wing-feather (fig. 44), thus excised. 



o°f female 8 "" corresponding featber Whilst flying from flower to flower 



he makes " a shrill, almost whist- 

 ling noise ;" 56 but it did not appear to Mr. Salvin that the noise 

 was intentionally made. 



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, /) 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 



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 con- 

 clusion 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 



55 Jerdon, ' Birds of India,' vol. 57 Sclater, in ' Proc. Zool. Soc.' 

 iii. pp. 618, 621. ' 1860, p. 90, and in 'Ibis,' vol. iv. 



56 Gould, 'Introduction to the 1862, p. 175. Also Salvin, in 

 Trochilida?,' 1861, p. 49. Salvin, < Ibis,' I06O. p. 37. 



4 Proc. Zoolog. Soc' 1867, p. 160. 



