118 GENERAL ORNITHOLOGY. 
the double-forked, a common style among saighgipers, as if each half of the tail were forked. 
But in such ease, the forking is slight, merely emargination, being little more than protrusion 
of the middle pair of feathers in an otherwise lightly forked tail; and in the double-rounded 
form the gradation is seldom if ever great. 
I should also allude to shapes of tail resulting from the relative positions of the feathers. 
Prominent among these is the complicate or folded tail of the barn-yard fowl, and others of the 
Phasianide, —-a very familiar but not common form. It is only retained while the tail is 
closed and cocked up, —for when it is lowered and spread in flight it flattens out. The oppo- 
site disposition of the feathers is seen to some extent in our crow blackbirds (Quwiscalus), 
where the lateral feathers 
slant upward from the lower- 
“~~ most central pair, like the 
—_____ sides of a boat from its keel; 
this is the scaphoid (Gr. 
oxadyn, a boat) or carinate 
(Lat. carina, a keel) tail. 
Our “boat - tailed” grackle 
_- has been so named on this 
By —— z =\ can account. One of the most 
e beautiful and wonderful of 
all the shapes of the tail is 
Fie. 33. — Diagram of shapes of tail. adc, rounded ; aec, gradate; ic, 
cuneate-gradate; alc, cuneate; abe, double-rounded; jeg, square; fhg, : 
emarginate; fneog, double-emarginate; kim, forked; kem, deeply forked; illustrated by the male of the 
kbm, forticate. lyre-bird (Menwra superba, 
fig. 82), in which the feathers are anomalous both in shape and in texture, and the resulting 
form of the whole is unique. Various shapes, which the student will readily name from the 
foregoing paragraphs, are illustrated in many other figures of this work. It should be remem- 
bered that, to determine the shape, the tail should be nearly closed; for spreading will ob- 
viously make a square tail round, an emarginate one square, ete. I append a diagram of the 
principal forms (fig. 33). 
IV. THE FEET. 
The Hind Limbs, in all birds, are organized for progression— all can walk, run, or hop 
on land, though the power to do so is very slight in some of the lower swimming birds, as 
loons and grebes, and certain of the lower perching birds, as hummers, swifts, goatsuckers, and 
kingfishers. They are specially fitted for perching on trees, bushes, and other supports requiring 
to be grasped, in the great majority of birds, as throughout the Passeres, Picarie, Accipitres, 
Columbe, and, in fact, many water-birds ; there being few forms, mainly found among three- 
toed birds, or those in which the hind toe is short, weak, and elevated, in which the extremity 
of the limb has not decided grasping power. The limb becomes a paddle for swimming either 
on or in the water in many cases. In not a few, as parrots and birds of prey, the foot is 
serviceable as a hand. Those kinds of birds which live in trees and bushes habitually 
progress, even when on level ground, in a series of hops, or rather leaps, both feet being 
moved together: in all the lower birds, however, the feet move one after the other, as in ordi- 
nary walking or running. The modifications of the hind limb are more numerous, more 
diverse, and more important in their bearing on classification than those of either bill, wing, 
or tail; their study is consequently a matter of special interest. 
Their Bony Framework (fig. 34). — Beginning at the hip-joint, and ending at the 
extremities of the several toes, the skeleton of the hind limb consists in the vast majority of 
adult birds of twenty bones. This is the typical and nearly the average number; birds 
