1 5 8 



ANIMAL BIOLOGY 



like the leaves of trees, are delicate structures and lose 



perfect condition with age. Hence the annual renewal 

 j of the feathers is 



an advantage. Most 

 birds shed twice a 

 year, and with many 

 the summer plum- 

 age is brighter col- 

 ored than the winter 

 plumage. When a 

 feather is shed on 

 one side, the corre- 

 sponding feather on 

 the other side is 



always shed with it. (What need for this ?) A large 



oil gland is easily found on the 



dorsal side of the tail. How does 



the bird apply the oil to the 



feathers ? 



FIG. 295. WING OF BIRD. 



/, false quills (on thumb) ; 2, primaries; j, secondaries: 

 tertiaries (dark) are one above another at right; 

 a, 6 t coverts. 



A 



FIG. 296. 



A , point dividing primaries from second- 

 aries; B, coverts. 



In describing and classifying 

 birds, it is necessary to know the 

 names of the various external 

 regions of the body and plum- 

 age. These may be learned by 

 studying Figs. 295, 296, 297, 298. 



FIG. 297. CEDAR WAXWING, 

 with regions of body marked. 



S, forehead; Sc, crown (with crest); 

 Hh, nape; A", throat; Br, breast; 

 Ba, lower parts; K, back; Rt, tail; 

 B, tail coverts; P, shoulder feathers 

 (scapulars) ; T, wing coverts; HS, 

 primaries; AS, secondaries; Al, 

 thumb feathers. 



The quills on the hand 



