50 Introduction. 



opposite points.' Moreover, the soles of its feet are remarkably 

 rough, and covered with protuberances, while the talons are very 

 much curved, sharp, and strong, that of the outer toe being the 

 largest, which is contrary to the usual custom ; and all these 

 peculiarities tend to the holding with greater security the slimy 

 victims on which it lives. 



The Nightjar, which feeds at twilight, presents another very 

 peculiar formation of foot. This is small and weak in proportion 

 to the size of the bird, but is remarkable for the claw of the 

 middle toe, which is particularly long and serrated, or pectinated, 

 on its inner edge, and resembles a comb with seven or eight 

 teeth. Now the food of the nightjar consists of moths, but 

 especially of fern-chaffers, beetles, and such late flying insects, 

 the legs of which are often terminated with hooked claws, to 

 detach which from the wide gaping mouth, and from the bristles 

 with which the upper mandible of the beak is fringed, this comb- 

 like claw is probably appended to the foot ; I say probably, for 

 much difference of opinion has existed with reference to its use. 

 Gilbert White, and others after him, thought they could perceive 

 the bird put out its short leg while on the wing and deliver 

 something into its mouth, and thus accounted for its use, that it 

 enabled the bird to hold more securely in its foot the insect it 

 had caught ; but for such a purpose it certainly seems but very 

 ill calculated. 



The Swift furnishes another instance of remarkable structure 

 of foot. As it passes the livelong day in unceasing and rapid 

 flight, it requires no great development of leg and foot ; thus the 

 tarsus is exceedingly short and thick, so short as to render the 

 bird incapable of rising from a flat surface, and therefore it never 

 alights on the ground. For rest and for incubation it retires to 

 the eaves of steeples and towers, to the perpendicular walls of 

 which, and to the face of cliffs, its foot is well adapted to cling ; 

 thus it consists of four toes, all of which are directed forwards, 

 and are armed with very hooked claws, and quite divided, and 

 which give it the appearance of belonging to a quadruped rather 

 than a bird. 



