BIRDS 



295 



yet flexible. They vary greatly in shape and also in number. The 

 swan, seeking its food under water, has a neck containing twenty- 

 three long vertebrae; the English 

 sparrow, in a different environ- 

 ment, has only fourteen short ones. 

 Some bones, notably the breast- 

 bone, are greatly developed in fly- 

 ing birds for the attachment of 

 the muscles used in flight. 



Bill. — The form of the bill 

 shows adaptation to a wonderful 

 degree. 



Skeleton of a fowl ; C, clavicle ; C. V., cer- 

 vical vertebrae; K., keeled sternum; 

 P.G., pelvic girdle; Pc.G., pectoral 

 girdle. 



Exercise for a Trip to a Museum or 

 Zoological Park. — Note a number of 

 different-shaped bills. How is the bill 

 adapted to taking the food for the bird ? 

 Seek for uses in each case. Remember 

 that a bird uses its bill as some ani- 

 mals use claws and teeth. Birds, ex- 

 cept the parrot and some of the birds 

 of prey, rarely use the claws in feeding. 

 The bills vary greatly according to the 

 habits of the birds. A duck has a flat 

 bill for pushing through the mud and 

 straining out the food; a bird of prey 

 has a curved or hooked beak for tear- 

 ing; the woodpecker has a sharp 

 straight bill for piercing the bark of 

 trees in search of the insect larvae which 

 are hidden underneath. 



Birds never have teeth, except possibly in the embryo stage. The edge of 

 the bill may be toothlike, as in some fish-eating ducks; these, however, are 

 not true teeth. Frequently, too, the tongue has sharp tooth like edges 

 which serve the same purpose as the recurved teeth of the frog or snako. 

 With care you may be able to make out the use of the tongue in eating 

 and drinking in some bird. Report in class the result of your observa- 

 tions. 



Reason for High Temperature and Rapid Heart Beat in Birds. — ]Make 

 observations on a bird as to the rapidity of the movements made in breath- 

 ing (respiratory movements). Compare them with your own as to rapidity. 

 Compare the rate of heart beat in your own body and that of a bird (a live 

 sparrow or canary). To take your own pulse, find the artery in your wrist 

 or on the side of your head about an inch above the midpoint, on a line 

 between the ear and eye. The heart of the bird may easily be felt by hold- 

 ing the hand against its breast. If now the temperature of the body of 

 the bird be taken (by holding a clinical thermometer under the wing), and 

 this compared with that of your own body taken under the arm, a con- 

 siderable difference will be noticed. 



