INTRODUCTION. xiii 



from the shoulder to the pinion joint ; this is known 

 scientifically as the Patagium. 



The legs are, in their way, almost as distinctive as the 

 wings. The true thigh is short and tucked up closely 

 to the body like the stifle-joint in a horse, to which it 

 corresponds. What is called the thigh in describing 

 a bird really corresponds to the leg of man from the 

 knee to the heel. 



The leg of the bird — the scaly part so called in popular 

 language — is really the elongated instep ; hence I 

 prefer the non-committal term of " shank " for it. The 

 term Tarsus, by which it is known ornithologically, 

 is incorrect, as well as being unintelligible to most 

 people. 



No bird has more than four toes, the fifth toe found 

 in some domestic fowls being a duplication of the 

 hinder toe. The usual arrangement of the toes is three 

 in front and one behind. This hind-toe corresponds 

 to the first or great toe in man, but in birds it is usually 

 the smallest of the four, often so small as to be useless, 

 and not infrequently absent altogether. The second toe 

 is often armed with a particularly large claw ; it is 

 absent in the Ostrich and in some Kingfishers. The 

 third toe, or middle front toe, sometimes has a toothed 

 edge to the inner side of the claw. This is, no doubt, 

 to increase its efficiency in scratching, as all birds 

 scratch themselves with this third toe. The outer toe is 

 absent only in a small Chinese Babbler {Cholornis 

 paradoxa). In many birds, however, as in Parrots 

 and Woodpeckers, it is turned backwards, thus throw- 

 ing the toes into two pairs. Such pair-toed birds often 

 lose the hind-toe, which shows that the disposition of 

 toes in pairs is no special adaptation to climbing. 



The toes may be altogether free — that is to say, not 

 connected by skin — or they may be more or less united 

 by a common skin, as in Kingfishers, or more or less 

 connected by a web or loose skin allowing of extension. 



