FORM AXI) ITAI'.IT: Tlir: WIXG. 23 



ine take y<»u iiiially t<> tlie j^oultrv yanl, wliere in the 

 wa(ldliii<]^ Duck yuu will see an undeniable instance of 

 deireneration. 



As the seat of sexual characters the wing is some- 

 times most singularly developed or adorned. The males 

 of the Argus Pheasant and Pennant- wingf'd Nightjar 

 have certiiin feathers enormously lengthened ; the IStand- 

 ard-bearer has white plumes gro\ving from the wing ; and 

 there are many other cases in wdiich the wing presents sex- 

 ual characters, not alone through display, but also by 

 use as a musical organ. I do not refer to the whistling 

 sound made by the wings of flying Doves or Ducks, or 

 the humming of llunnningbirds, but to sounds volun- 

 tarily produced by birds, and evidently designed to an- 

 swer the purpose of song. 



A simple form of this kind of " music " is shown by 

 the cock in clapping his wings before crowdng, in the 

 "drumming" of Grouse, or in the " booming" of Night- 

 hawks, as w^ith wings set they dive from a height earth- 

 ward. The male Cassique {Ostinojys) of South America, 

 after giving voice to notes which sound like those pro- 

 duced by chafing trees in a gale, leans far forward, 

 spreads and raises his large orange and black tail, then 

 vigorously claps his wings together over his back, mak- 

 ing a noise which so resembles the cracking of branches 

 that one imagines the birds learned this singular per- 

 formance during a gale. 



The birds mentioned thus far have no especial w4ng 

 structure beyond rather stiffened feathers ; but in the 

 Woodcock, some Paradise-birds and Flycatchers, Guans, 

 Pipras, and other trojiical birds, certain wing-feathers 

 are singularly modified as nnisical instruments. Some- 

 times the outer ])rimaries are so narrowed that little but 

 the shaft or midrib is left, as in both sexes of the Wood- 

 cock, when the rapid wing-strokes are accompanied l)y a 



