3/8 The Descent of Man. Pakt II. 



The male alone of, one of the Indian bustards {Syplieotides 

 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.^^ 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 tha 

 webs abruptly excised towards 

 the extremity. The male, for in- 



Kig. 44. Primary wing-featlier of a stance, of Htlasphorus platycercus, 

 Hiimmmg-bh-d, the Helasphorus pla. _u„_ „^,-,u hfiq thp first nri mi vt/ 



tycercus (from a sketcii by Mr. Sal- ^nen aauit, nas me nrsx primal y 



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



o«emif."'" "^""'^P""*'"" ''''''"'' Whilst flying from flower to flower 

 he makes " a shrill, almost whist- 

 ling noise ;" ^° 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 secoz/rfacs/ wing- 

 feathers modified in a still more remarkable manner. In the 

 brilliantly-coloured P. delicio^a 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 (h, 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 

 ('^> «j /) in the female. Even the bones of the wing, which 

 support these singular feathers in the male, are said by Mr. 

 Eraser to be much thickened. These little birds make an 

 extraordinary noise, the first " sharp note being not unlike the 

 " crack of a whip." ^'' 



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, prinirr'ly used as a 

 mere call or for some other purpose, might have been improved 



" Jerdon, ' Birds of India,' vol. " Sclater, in ' Proc. Zool. See' 



iii. pp. (518, 621. I860, p 90, and in 'Ibis,' vol. iv. 



=° Gould, ' Jntrodiiction to the 1862, p. 17.5. Also Salvia, in 



Trochilida,' 1861, p. +9. Salvin, ' Ibi^,' 1860, p. 37. 

 'Proc. Zoolog. See' 1867, p. 160. 



