SEC. Ill EXTERIOR PARTS OF BIRDS 183 



35). The toes themselves are feathered in a few birds, as several of 

 the owls, and all the ptarmigans (Lagopus). Partial feathering of 

 the tarsus is often continued downward, to the toes or upon them, 

 by sparse modified feathers in the form of bristles ; as is well shown 

 in the barn-owl (Fig. 47). When incomplete, the feathering is 

 generally wanting behind and below, and it is almost invariably 

 continuous above with the crural plumage. But in that spirit of 

 perversity in which birds delight to prove every rule we establish 

 by furnishing exceptions, the tarsus is sometimes partly feathered 

 discontinuously. A curious example of this is afforded by the bank- 

 swallow, Cotile rvparia, with its little tuft of feathers at the base of 

 the hind toe ; and some varieties of the barn-yard fowl sprout mon- 

 - strous leggings of feathers from the side of the tarsus. 



The Length of Leg, relatively to the size of the bird, is ex- 

 tremely variable ; a thrush or sparrow probably represents about 

 average proportions of the limb. The shortest-legged bird known 

 is probably the frigate-pelican (Tachypetes) ; which, though a yard 

 long, more or less, has a tibia not half as long as the skull, and a 

 tarsus under an inch. The leg is very short in many Picarian birds, 

 as hummers, swifts, goatsuckers, kingfishers, trogons, etc., in most 

 of which it scarcely serves at all for progression. Among Passeres, 

 the swallows resemble swifts in shortness of their hind limbs. It 

 is pretty short likewise in many zygodactyl, yoke-toed, or scansorial 

 birds, as woodpeckers, cuckoos, and parrots. In most swimming 

 birds the limb may also be called short, especially in its femoral 

 and tarsal segments ; while the broad-webbed toes are comparatively 

 longer. The leg lengthens in the lower perching birds, as many 

 hawks and some of the terrestrial pigeons ; it is still longer among 

 walkers proper, such as the gallinaceous birds, and reaches its 

 maximum among the waders, especially the larger ones, such as 

 cranes, herons, ibises, storks, and flamingoes; among all of which 

 it is correlated with extension of the neck. Probably the longest- 

 legged of all birds for its size is the stilt {Eimantopus). Taking 

 the tarsus alone as an index of length of the whole limb, this is in 

 the frigate under one-thirty-sixth of the bird's length ; a flamingo, 

 four feet long, has a tarsus a foot long; a stilt, fourteen inches 

 long, one of four inches; so that the maximum and minimum 

 lengths of tarsus are nearly thirty and under three per cent of a 

 bird's whole length. 



The Horny Integument of the Foot requires particular atten- 

 tion. That part of the limb which is devoid of feathers is covered, 

 like the bill, by a hardened, thickened, modified integument, vary- 

 ing in texture from horny to leathery. This sheath is called the 

 podotheca (Gr. ttovs, iroSo's, pous, podos, foot, and ^ijkij, theke, sheath). 

 It is more corneous in land birds, and in water birds more leathery ; 



