20 



A BOOK OF BIRDS 



the claws may be used as a weapon of offence. In this bird the inner 

 claw is of great size and strength, and is capable of inflicting a very 

 dangerous wound. 



In many of the Grouse tribe the claws are shed each spring ; 

 though in some, as in the Black Game, the shedding is confined to 

 the ragged fringe along the inner side of the claws. This fringe, 

 by-the-bye, recalls the fact that the middle claw in many birds, as 

 the Barn Owl, Nightjar, and Herons, for instance, has a curious 

 series of little teeth running along its outer edge ; but so far no one 

 has been able to tender any suggestion as to what purpose it may serve. 



Finally we must find space for a brief reference to the formidable 

 weapons which many birds possess in the shape of spurs. These are 

 generally confined to the legs, and may be represented by a pair only, 

 as in the Game-cock, or by several, as in the Peacock-pheasant. 

 But beside these, a few birds have a similar, and equally powerful, 

 armature in the wings. In some, as on the " Screamers " (Pala- 

 medea and Chauna), two spurs are developed, one at each end of 

 the fused metacarpal bones — the bones which form the ** palm " of 

 the hand ; in all other birds but one spur is developed, and this may 

 spring from one of the wrist-bones, as in the Spur-winged Goose, or 

 from the base of the thumb, as in the Jacanas. 



Flight and its Mechanism.— While, in the possession of feathers, 

 birds occupy an absolutely unique position in the animal kingdom, 

 they are not to be so distinguished in the matter of their flight, for 

 many creatures far below them in the scale of life are no mean per- 

 formers in this most enviable form of locomotion ; while the Bats, 

 which belong to the man's own class — the Mammalia — on the other 

 side of the scale, are also adepts in the art. In the manner of 

 their flight, at any rate, the birds are peculiar, though, for the matter 

 of that, so also, it may be urged, are the Butterflies and Bats. But, 

 as we shall show, this is not altogether true. 



In the study of '' the way of the bird in the air," so many factors 

 have to be taken into consideration that it is difficult to know where 

 to begin, and even then, having made a beginning, it is by no means 

 easy to make a plain, straight-forward tale of it. Technicalities will 

 seem to thrust themselves in upon our argument, with many specious 

 promises of making things clearer ; but they shall be severely re- 



