FORM AND HABIT: THE TAIL. 25 



have fonnidaljle spurs on their wings, wliifli tliey are 

 snpposeil to use in combat. 



Tlic Tall. — Except when sexually developed, the 

 shape of tlie tail is largely governed by the character 

 of its owner s flight. Male Lyre-birds, Pheasants, Fowls, 

 Hummingbirds, and many others furnish well-marked 

 instances of the tail as a sexual character. Indeed, as 

 the least important to the bird of the four external 

 organs we are speaking of, the tail is more (.)ften sexually 

 modified than any of the other three. 



The main office of the tail, however, is mechanical, to 

 act as a rudder in flight and a " balancer " when perch- 

 ing. Short-tailed birds generally fly in a straight course, 

 and can not make sharp turns, while long-tailed birds can 

 pursue a most erratic course, with marvelous ease and 

 grace. The Grebes are practically tailless, and their 

 flight is comparatively direct, but the Swallow-tailed 

 Kite, with a tail a forjt or more in length, can dash to 

 right or left at the most abrupt angle. 



Among tree-creeping birds, which always climb up- 

 ward, the tail is used as a brace or prop. This character, as 

 has been said, is possessed by all Woodpeckers, Ijy the cpute 

 different Woodhewers of South America, the Brown Creep- 

 ers of temperate regions, and other liirds (see Figs. 3 and 4). 



The two middle feathers in the tail of the Motmot, 

 of the American tropics, end in a racket-shaped disk, the 

 result of a unicpie habit. Similarly shaped feathers are 

 found in the tails of some Hummingbirds and Old World 

 Kingfishers, but in the Motmot this peculiar shape is due 

 to a self-inflicted mutilation. The newly grown feathers, 

 as shown in the accompanying figure, lack the terminal 

 disk, but as soon as they are grown, the birds begin to 

 pick at the barbs, and in a short time the shaft is de- 

 nuded, in some species tor the space of an inch, in others 

 for as much as two inches. 



