Fig. 298.—Plan of Bird.
s, centre of gravity.
Fig. 299.—Position of Limbs of Pigeon.
Control of Flight.—Did you ever see a bird sitting on a swinging limb? What was its chief means of balancing itself? When flying, what does a bird do to direct its course upward? Downward? Is the body level when it turns to either side? Birds with long, pointed wings excel in what respect? Examples? Birds with great wing surface excel in what kind of flight? Examples. Name a common bird with short wings which has a laboured, whirring flight. Is its tail large or small? Does it avoid obstacles and direct its flight well? Why or why not? When a boat is to be turned to the right, must the rudder be pulled to the right or to the left? (The rudder drags in the water and thus pulls the boat around.) When the bird wishes to go upward, must its tail be turned up or down? How when it wishes to go down? When a buzzard soars for an hour without flapping its wings, does it move at a uniform rate? For what does it use the momentum gained when going with the wind?
Fig. 300.
a, clambering foot of chimney sweep; b, climbing foot of woodpecker; c, perching foot of thrush; d, seizing foot of hawk; e, scratching foot of pheasant; f, stalking foot of kingfisher; g, running foot of ostrich; h, wading foot of heron; i, paddling foot of gull; k, swimming foot of duck; l, steering foot of cormorant; m, diving foot of grebe; n, skimming foot of coot. Question: Does any bird use its foot as a hand? (Fig. [320].)
Flying.—When studying the quill feathers of the wing, you saw that the wider side of the vane is beneath the feather next behind it. During the downward stroke of the wing this side of the vane is pressed by the air against the feather above it and the air cannot pass through the wing. As the wing is raised the vanes separate and the air passes through. The convex upper surface of the wing also prevents the wing from catching air as it is raised. Spread a wing and blow strongly against its lower surface; its upper surface. What effects are noticed?
Study the scales on the leg of a bird (Fig. [300]). Why is the leg scaly rather than feathered from the ankle downward? Which scales are largest? (Fig. [300].) How do the scales on the front and the back differ? What can you say of the scales at the bottom of the foot; at the joints of the toes? Explain. How does the covering of the nails and the bill compare in colour, texture, hardness, and firmness of attachment with the scales of the leg?
