EXTERIOR PARTS OF BIRDS 



193 



foundly, or, if united at base, it is by movable webbing ; the claws 

 are immensely developed, and the under surfaces of the toes are 

 scabrous or bulbous for greater security of the object grasped. Any 

 hawk or owl or old-world vulture exhibits the raptorial or inses- 

 sorial foot (Figs. 46, 47). 2. The cursorial or grallatorial type. The 

 gist of this plan lies in the decrease or entire loss of the grasping 

 function, and in the elevation, reduction in length, or loss of the 

 hind toe ; the foot is a good foot, but nothing of a hand. The 

 columbine birds, which are partly terrestrial, partly arboreal, ex- 

 hibit the transition from the perching to the gradient foot, in some 

 reduction of the hind toe, which is nevertheless in most cases still 

 on the same level as the rest (Fig. 38, h). In the gallinaceous or 

 rasorial (Lat. rasor, a scraper) birds, which are essentially terrestrial, 

 and noted for their habit of scratching the ground for food, the 



Fig. 4". — Raptorial foot of an owl, Aluco flamitieus, nat. size. From nature by Coues. 



hind toe is decidedly elevated and shortened in almost all of the 

 families (Fig. 35). Such reduction and uplifting of the hallux is 

 carried to an extreme in most of the waders, or Gi-allatores, in many 

 of which this toe disappears (Figs. 38 a, 39). It is scarcely practic- 

 able to recognise special modifications of such gradient or gralla- 

 torial feet, since they merge insensibly into one another. The herons, 

 which are the most arboricole of the waders, exhibit a reversion to 

 the insessorial type, in the length and incumbency of the hallux. 

 The mode of union of the front toes of the walkers and waders is 

 somewhat characteristic. The toes are either cleft quite to the 

 base, or there joined by small webs ; probably never actually 

 coherent. Such basal webbing of the toes is called semipalmation 

 ( "half- webbing "). It is actually the same thing that occurs in 

 many birds of prey, in most gallinaceous birds, etc. ; the term is 

 mostly restricted, in descriptive ornithology, to those loading birds, 

 or Grallatorcs, in which it occurs. Such basal webs generally run out 







