106 



USES OF THE WING 



Auks and other members of their family fly under water and some 

 Ducks also use their wings when diving, while the true Divers use both 

 feet and wings. (See Townsend, The Auk, and "A Labrador Spring," pp. 

 180-205.) The loss by molting, depriving birds of all their flight- 

 feathers at the same time, has already been mentioned (see Molt), 



FIQ. 15. Man-'o-war-bird; a species in which the wings have been developed 

 at the expense of the feet. 



and it will be interesting to learn whether at this time the Auks use their 

 feet when progressing under water or whether a wing devoid of its 

 quills supplies sufficient power. Young birds rest upon their wings as 

 they would upon fore-feet and in some instances (e. g. Grebes and Galli- 

 nules) they are employed in climbing about among reeds, etc., or with 

 young Herons, among branches. Adult Grebes and Loons, like the 

 flightless Penguins, rely on their wings to aid them when on land. 



The whistling or humming of wings may be the accompaniment 

 of regular flight, as with the Mourning Dove, certain Ducks, or the 

 Hummingbirds; it may be the result of an especial evolution, as with 



the swooping Nighthawk, or 

 it may proceed from some 

 special structure, as with the 

 narrowed outer primaries of 

 the Woodcock. The drum- 

 ming of Grouse and the 

 'clapping' of Roosters, before 

 crowing, are further illustra- 



FIQ. 16. The wing as a musical organ. Wing tions of the US6 of the wing as 

 of Woodcock, showing outer attenuate feathers ^ musical organ 

 which produce the 'whistling' sound in flight. or^- TT , 



Sitting Hens threaten with 



their wings, Swans and Pigeons strike with them, Herons use the wing 

 as a shield, altricial birds protect their young from sun or rain by 

 standing over them with spread wings, and they shelter praecocial 

 birds; fledglings flutter the wings tremulously when begging for food. 



The Tail. A bird's tail is primarily a rudder. Compare the direct 

 line of flight of a short-tailed bird, for example, a Duck or Quail, with 

 the darting, erratic movements of a Tern or Barn Swallow. Soaring 

 birds spread the tail as an additional means of support and balance; 

 and when spread and thrown downward and forward it serves as a 

 brake for the bird when alighting. 



