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), 
Fia. 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 
ae ‘clapping’ of Roosters, before 
NRO ESS, crowing, are further illustra- 
4 
Fria. 16. The wing as a musical organ. Wing tions of the use of the wing as 
ot ocdagols a oming awe Pee fe tees a musical organ. 
which produce the ‘whistling’ sound in flight. ange 7 ; 
i . yes 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 precocial 
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. 
