Ears.—Do birds have external ears? Is there an external opening leading to the ear? In searching for it, blow or push forward the feathers. If found, notice its location, size, shape, and what surrounds the opening. There is an owl spoken of as the long-eared owl. Are its ears long?
The leg has three divisions: the uppermost is the thigh (called the “second joint” in a fowl); the middle division is the shank (or “drumstick”); and the lowest, which is the slender bone covered with scales, is formed by the union of the ankle and the instep. (The bones of the three divisions are named femur, tibiotarsus, and tarsometatarsus.) The foot consists entirely of toes, the bones of which are called phalanges. Is there a bone in each claw? (See Fig. [285].) Supply the numerals in this sentence: The pigeon has ____ toes, the hind toe having ____ joints; of the three front toes, the inner has ____ joints (count the claw as one joint), the middle has ____ joints, and the outer toe has ____ joints (Fig. [285]). Is the thigh of a bird bare or feathered? The shin? The ankle? Where is the ankle joint of a bird? Do you see the remains of another bone (the splint bone, or fibula) on the shin bone of the shank? (Fig. [285] or 286.) Why would several joints in the ankle be a disadvantage to a bird?
Fig. 285.—Leg Bones of Bird.
Fig. 286.—Skeleton of Bird.
Rh, vertebræ; Cl, clavicle; Co, coracoid; Sc, scapula; St, sternum; H, humerus; R, radius; U, ulna; P, thumb; Fe, femur; T, tibia. See Fig. [394].
Questions: Which is the stiffest portion of the vertebral column? How are the ribs braced against each other? Which is longer, thigh bone or shin? Compare shoulder blade with man’s (Fig. [399]). Which is the extra shoulder bone? Compare tail vertebræ with those of extinct bird, Fig. [290].
The thigh hardly projects beyond the skin of the trunk, as may be noticed in a plucked fowl. The thigh extends forward from the hip joint (Figs. [286], [299]) in order to bring the point of support forward under the centre of weight. Why are long front toes more necessary than long hind toes? As the bird must often bring its head to the ground, the hip joints are near the dorsal surface and the body swings between the two points of support somewhat like a silver ice pitcher on its two pivots. Hence stooping, which makes a man so unsteady, does not cause a bird to lose steadiness.
Fig. 287.—Hand and Wrist of Fowl (after Parker).
DG. 1–3, digits; MC. 1–3, metacarpals; CC. 3, wrist.
The wing has three divisions which correspond to the upper arm, the forearm, and the hand of man (Fig. [286]). When the wing is folded, the three divisions lie close alongside one another. Fold your arm in the same manner. The similarity of the bones of the first and second divisions to the bones of our upper arm and forearm is very obvious (Fig. [286]). Explain. The hand of a bird is furnished with only three digits (Fig. [287]). The three palm bones (metacarpals) are firmly united (Fig. [287]). This gives firmness to the stroke in flying.