EXTERNAL PABTS OF BIRDS. — THE FEET. 
123 
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 
snipe 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 
fig. 36) in the vast majority of birds is entirely naked, being provided with a horny or leathery 
sheath of integument like that covering the bill. Such is its condition in the Passeres and 
Picarics (with few exceptions, as among swifts and goatsuckers) ; in the waders without ex- 
ception, and in nearly all swimmers (the frigate-bird, Tachypetes, has a slight feathering). 
The Baptores and GalUncs 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, Falco, 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 (Lagopus). 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 
birds delight to 
prove every rule ~ Feathered tarsus of a grouse, Cupidonia cupido. Nat. size, 
we establish by furnishing exceptions, the tarsus is sometimes partly feathered discontinuously. 
A curious example of this is afforded 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 bird, is extremely 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 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 likewise in many zygodactyle, 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 stiU 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 wdth 
extension of the neck. Probably the longest-legged of aU birds for its size is the stilt 
{Himantopus). 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 
