EXTERNAL PARTS OF BIRDS. — THE FEET. 



129 



the walking and especially the wading birds that the cms is most extensively denuded ; 

 it may be naked half-way up to the knee. A few waders, — among ours, chiefly in the 

 sniije family,— have the crus apparently clothed to the heel-joint; but this is due, in most if 

 not all cases, to the length of the feathers, for probably in none of them does the pteryla cruralis 

 itself extend to the joint. Crural feathers are nearly always short and inconspicuous; but 

 sometimes long and flowing, as in the " flags " of most hawks, and in our tree-cuckoos. The 

 tarsus (I now and hereafter use the term in its ordinary acceptation — C to D in fig. 34; trs in 

 fii?. 36) in the vast majority of birds is entirely naked, being provided with a horny or leathery 

 sheath of integument like that covering the bUl. Such is its condition in the Passeres and 

 PicaricB (with few exceptions, as among swifts and goatsuckers) ; in the waders without ex- 

 ception, and in nearly all swimmers (the frigate-bird, Tachtjpetes, has a slight feathering). 

 The Raptores and GaUinee furnish the most feathered tarsi. Thus, feathered tarsi is the rule 

 among owls (Striges) ; frequent, either partial or complete, in hawks and eagles, as in Aquila, 

 Archibuteo, Fulco, Buteo, etc. All our grouse, and perhaps all true grouse, have the tarsus 

 more or less feathered (fig. 35). The toes themselves are feathered in a few birds, as several 

 of the owls, and all the ptarmigans {Lagopiis). Partial feathering of the tarsus is often con- 

 tinued 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 want- 

 ing behind and 

 below, and it is 

 almost invariably 

 continuous above 

 with the crural 

 plumage. But in 

 that spirit of per- 

 versity in which 

 })lrds delight to 

 I)rove every rule Fig. 35. —Feathered tarsus of a grouse, CMpirfaniacajsirfo. Nat. size. 



we establish by furnishing exceptions, the tarsus is somethnes partly feathered discontinuously. 

 A curious example of this is afi"orded by the bank-swallow, Cotile riparia, with its little tuft of 

 feathers at the base of the hind toe ; and some varieties of the barn-yard fowl sprout monstrous 

 leggings of feathers from the side of the tarsus. 



The Length of Leg, relatively to the size of the bii'd, is extremely variable ; a thrush or 

 sparrow probably re]iresents about average proportions of the limb. The shortest-legged bird 

 known is probably the frigate-pelican, Tachy petes ; 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 Picariau birds, as hummers, swifts, goatsuckers, kingfishers, trogons, etc., in many 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 likemse in many zygodactyle, yoke-toed or 

 scansorial birds, as woodpeckers, cuckoos, and paiTots. 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 maxinmm 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 

 {Himantopus). Taking the tarsus alone as an index of length of tlie 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 louijc, one of four inches; so that the maximum and 



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