362 ELEMENTARY ZOOLOGY 



others that in some instances (young hawks) an infusion 

 or loss, as the case may be, of pigment takes place as the 

 feather forms, and continues so long as it grows." 



There is much lack and uncertainty of knowledge con- 

 cerning the molting and change of plumage by birds, and 

 careful observations by bird-students should be made on 

 the subject. 



In connection with learning the different kinds of birds 

 in a locality, together with their names, observations 

 should be made, and notes of them recorded, on their 

 habits and on the relation or adaptation of structure and 

 habit to the life of the bird. Some of the special subjects 

 for such observation are pointed out in the following 

 paragraphs. A suggestive book, treating of the adapt- 

 ive structure and the life of birds is Baskett's "The 

 Story of the Birds." 



Bills and feet. The interesting adaptation of struc- 

 ture to special use is admirably shown in the varying 

 character of the bills and feet of birds. The various feed- 

 ing habits and uses of the feet of different birds are readily 

 observed, and the accompanying modification of bills 

 and feet can be readily seen in birds either freshly killed 

 or preserved as "bird-skins." Such skins may be made 

 as directed on p. 467, or may be bought cheaply of 

 taxidermists. A set of such skins, properly named, will 

 be of great help in studying birds, and should be in the 

 high-school collection. In some cases the general struc- 

 ture of feet and bills may be seen in the live birds by the 

 use of an opera-glass. The characters of bills and feet 

 are much used in the classification of birds, so that any 

 knowledge of them gained primarily in the study of 

 adaptations will have a secondary use in classification work. 



Note the foot of the robin, bluebird, catbird, wrens, 

 warblers and other passerine or perching birds. It has 

 three unwebbed toes in front, and a long hind toe per- 



