C2 SEXUAL SELECTION: BIRDS. [I'akt II. 



rushing noise," like the lulling of a tree." The male alone 

 of one of the Indian bustards {ISypheotkles anritus) has its 

 l)riinary wing-feathers greatly acuminated; and the male 

 of an allied speeies is known to make a humming noise 

 while courting the female." In a widely-different group 

 of hirds, namely the Huniming-hirds, the males alone of 



certain kinds have either the 

 shafts of their primary wing- 

 feathers broadly dilated, or the 

 webs abruptly excised toward 

 the extremity. The male, for 

 F.r n.-i',inu.r.y win^.A.uiu r of instance, of ^Selaspho7-us 2)l((fu- 



a Humnuug-bird, the Selaxplto- ■' I if 



rus i)iattjctrcm (from a sketch cercxs, when adult, has the 

 by Mr. saivin). Upper flgurc, first primary winfj-foather (Fig. 



that of male ; lower lignre, cor- ..n .*,.,. \ o 



responding feather of female. '^'^) excised m this manner. 

 While flying from flower to 

 flower he makes "a shrill, almost.whistling noise;"" but 

 it did not a])pear to Mr. tsalvin that the noise was inten- 

 tionally made. 



Lastly, in several species of a sub-genus of Pipra or 

 Manakin, the males have their secondare/ wung-feathers 

 modified, as described by Mr. Sclater, in a still more re- 

 markable manner. In the brilliantly-colored J*, deltciosa 

 the first three secondaries are thick-stemmed and curved 

 toward the body ; in the fourth and fifth (Fig. 45, a) the 

 change is greater ; and in the sixth and seventh (?>, c) the 

 shaft " is thickened to an extraordinary degree, forming a 

 solid horny lump." Tlie barbs also are greatly changed, 

 in shape, in comparison with the corresponding feathers 



"* Mr. Saivin, in ' Proc. Zool. Soc' 186Y, p. 160. I am much indebted 

 to this distinguished ornithologist for sketches of the feathers of the 

 Chamtcpetcs, and for other information. 



" Jerdon, 'Birds of India,' vol. iii. pp. 618, 621. 



** Gould, 'Introduction to the Trochilidae,' 18G1, p. 40. Saivin, 

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



