82 ANIMAL BIOLOGY 



especially characteristic of the perching birds. For this reason, the 

 birds in this, the highest order, are known as "birds of passage." 



FIG. 71. The robin. 



65. Field work on birds. Pupils should become familiar with 

 the size, form, colors, and song of as many birds as possible, and 

 should note carefully where each kind of bird is most commonly 

 found (e.g. in marshes, trees, bushes, or on the ground). In this 

 study bird glasses or opera glasses are very useful. Books like 



1 Length of robin from tip of bill to tip of tail feathers, about 10 

 inches; length of sparrow from tip of bill to tip of tail feathers, 

 fcbout 6 inches. 



