24 BIRD FRIENDS 



different robins and different orioles through their 

 songs. 



There may also be a variation in the song of any 

 one individual, dependent on age and season. The 

 first efforts of the young bird to sing are not so near 

 the type of that species as those which he makes in 

 later seasons. Again the song of the individual may 

 change as the season progresses, the song becoming 

 shorter and shorter till it ceases altogether. 



Mr. Oldys reports that he has noted more than 

 eighty different wood thrush phrases, and he says 

 that song sparrows' phrases are more diverse than 

 those of wood thrushes. A song sparrow has been 

 known to render twelve distinct themes in fifteen 

 minutes. 



Individual differences are due, not only to the 

 use of different phrases, but also to the way in which 

 the phrases are rendered. There may be excellent 

 rendering and poor rendering of the same phrase 

 among birds, just as there are varying degrees of 

 excellence among human voices. 



Range of voice. A study of the records made of 

 bird songs suggests the pitch and range for different 

 birds. The tones of nearly all birds are high-pitched, 

 ranging between two and four octaves above middle 

 C. The range of voice in different species varies 

 from three notes for the chickadee to two octaves 

 for the hermit thrush. A number of birds have a 

 range of about one octave. 



