How Birds Fly

Teacher’s Story

O convince the children that a bird’s wings correspond to our arms, they should see a fowl with its feathers off, prepared for market or oven, and they will infer the fact at once.

The bird flies by lifting itself through pressing down upon the air with its wings. There are several experiments which are needed to make the child understand this. It is difficult for children to conceive that the air is really anything, because they cannot see it; so the first experiment should be to show that the air is something we can push against or that pushes against us. Strike the air with a fan and we feel there is something which the fan pushes; we feel the wind when it is blowing and it is very difficult for us to walk against a hard wind. If we hold an open umbrella in the hand while we jump from a step we feel buoyed up because the umbrella presses down upon the air. The bird presses down upon the air with the wings, just as the open umbrella does. The bird flies by pressing down upon the air with its wings just as a boy jumps high by pressing down with his hands on his vaulting pole.

Study wing and note: (a) That the wings open and close at the will of the bird. (b) That the feathers open and shut on each other like a fan. (c) When the wing is open the wing quills overlap, so that the air cannot pass through them. (d) When the wing is open it is curved so that it is more efficient, for the same reason that an umbrella presses harder against the atmosphere when it is open than when it is broken by the wind and turned wrong side out.

A wing feather has the barbs on the front edge lying almost parallel to the quill while those on the hind edge come off at a wide angle. The reason for this is easy to see, for this feather has to cut the air as the bird flies; and if the barbs on the front side were like those of the other side they would be torn apart by the wind. The barbs on the hind side of the feather form a strong, close web so as to press down on the air and not let it through. The wing quill is curved; the convex side is up and the concave side below during flight. The concave side, like the umbrella, catches more air than the upper side; the down stroke of the wing is forward and down; while on the up stroke, as the wing is lifted, it bends at the joint like a fan turned sidewise, and offers less surface to resist the air. Thus, the up stroke does not push the bird down.

Observations should be made on the use of the bird’s tail in flight. The hen spreads her tail like a fan when she flies to the top of the fence; the robin does likewise when in flight. The fact that the tail is used as a rudder to guide the bird in flight, as well as to give more surface for pressing down upon the air, is hard for the younger pupils to understand, and perhaps can be best taught by watching the erratic unbalanced flight of young birds whose tail feathers are not yet grown.

The tail feather differs from the wing feather in that the quill is not curved, and the barbs on each side are of about equal length and lie at about the same angle on each side the quill. See Fig. p. 28.

References—The Bird Book, Eckstorm, pp. 75–92; Story of the Birds, Baskett, pp. 171–176; Bird Life, Chapman, p. 18; The Bird, Beebe, Ch. XIII; First Book of Birds, Miller.