14 BIRD BEHAVIOUR 



Pipits, Larks, and Starlings. As passerine birds 

 are all primarily adapted for a life in trees, even the 

 Larks still having a typical percher's foot, and as 

 jumping from bough to bough is a natural and 

 habitual movement, it seems natural that this 

 should be continued in all except those most 

 thoroughly adapted to a ground life. 



The same reasoning applies to the Hornbills, 

 among which family are to be found the only large 

 birds which hop ; there are two species of this 

 usually very short-legged and highly arboreal family 

 which have legs of the ordinary length and live 

 mostly on the ground, the Ground-Hornbills (Bu- 

 corax), and these move their legs alternately in 

 the ordinary walking fashion and are even able to 

 run well, which some walking birds do not do 

 most Herons and Storks, for instance. In the case 

 of these Hornbills, it is to be noted that the hind 

 toe is just as well developed as in the perching 

 kinds, and that they walk on the end joints of the 

 toes, the ball of the foot being raised above the 

 ground, so that one could put a marble under it. 

 This would be unique among birds, which usually 

 tread on the whole under-surf ace of the toes, where 

 these are on the same level i.e. the hind toe not 

 set on higher were it not for the case of the 

 Ostrich, which lifts the basal joints of its two 

 toes off the ground even more, so that its foot can 

 fairly be said to have a pastern-joint, like that of the 

 hoofed beasts with which it habitually grazes. In 

 the Ostrich reduction of the toes is carried to an 



