366 ELEMENTARY ZOOLOGY 



Varying even more than the mariner and power of 

 flight among different birds are the vocal utterances, the 

 cries and calls and singing. By their calls and songs 

 alone many birds may be identified although they remain 

 unseen. The field-student of birds comes to know them 

 by their songs; knows what birds they are; knows what 

 they are doing or not doing; knows what time in their 

 life-season it is, whether they are mating, or brooding, or 

 preparing to migrate; knows whether they are frightened, 

 or self-confident, whether in distress or happy. Little 

 urging and suggestion are needed to induce the student 

 to attend to the songs. But the naturalist should not 

 only hear and enjoy them, but by observation and the 

 recording of repeated observations, he should come to 

 understand the significance of the calls and songs. 



As to how these sounds are made, attention has already 

 been called (see p. 338) to the voice-organ or syrinx. 

 The condition of this organ varies much in birds, as 

 would be expected from the differing character of vocal 

 utterances. Dissections will make these differences 

 apparent. 



Nesting and care of young. Among the birds' most 

 interesting instincts and habits are those domestic ones 

 which include mating, nest-building, and care of the 

 young. Birds' eggs and birds' nests are always attrac- 

 tive objects of search and collection for boys, and most 

 boys have a considerable personal knowledge of the 

 domestic habits of the commoner summer birds of their 

 region. With this interest and unsystematized knowledge 

 as a basis the teacher should be able to get from the class 

 much excellent field-work and personal observation. The 

 first thing to undertake in this study is the gathering of 

 data regarding the character of the nests of different 

 species, their situation, the time of nesting, the participa- 

 tion or non-participation of the male in nest-building, 



