34 Handbook of Nature-Study 



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 con- 

 cave side below during flight. The concave side, like the umbrella, 

 catches more air than the upper side ; the down stroke of the wing is for- 

 ward 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. 



LESSON III. 



How BIRDS FLY 



Leading thought A bird flies by pressing down upon the air with its 

 wings, which are made especially for this purpose. The bird's tail acts as 

 a rudder during flight. 



Method The hen, it is hoped will by this time be tame enough so that 

 the teacher may spread open her wings for the children to see. In addi- 

 tion, have a detached wing of a fowl such as are used in farm houses 

 instead of a whisk-broom. 



Observations i. Do you think a bird's wings correspond to our 

 arms? If so why? 



2. Why do birds flap their wings when they start to fly? 



3. Can you press against the air with a fan? 



4. Why do you jump so high with a vaulting pole? Do you think 

 the bird uses the air as you use the pole? 



5. How are the feathers arranged on the wing so that the bird can 

 use it to press down on the air? 



