134 Stkong, The Voice of Birds. [^ 



It is my practice to subject the vocal performances of birds to 

 analyses which may be employed with the voice of other groups of 

 animals. In fact, some of my first ideas on the subject came from 

 a study of methods used by Professor Reighard of the University 

 of Michigan, in studying the voice of frogs and toads. 



The following features are of first importance, in my experience, 

 when the voice of a bird is heard for the first time: duration, 

 quality, loudness, general pitch, complexity, accent, stress, and 

 relation to known sounds. 



Under duration, we note the time occupied by a vocal perform- 

 ance. If simply a chirp, for instance, we indicate whether it is 

 short or relatively long. Longer performances are measured in 

 seconds, the number of which is usually surprisingly less than would 

 be estimated without timing. 



Quality is of course important, and it may be described in many 

 ways. One of the first things I have students do is to observe 

 whether the sound is relatively musical or unmusical. Some bird 

 sounds are not easily classed as either, but a great number can be 

 so distinguished. Thus, I find no one hesitating to call the voice 

 of the Wood Thrush musical and that of the Kingbird unmusical. 



The first time I take up bird song with students, I discuss the 

 relation of overtones to quality of sound and some other principles 

 of physics pertinent to the subject. Such terms as rich, thin, bell- 

 like, flute-like, resonant, reedy, metallic, rasping, harsh, etc., are 

 helpful in describing quality. It is also very useful to make com- 

 parisons with other known sounds. 



Under general pitch, we observe whether the voice is relatively 

 high or low in pitch. As might be expected, the results are variable, 

 but the effort is worth while in establishing associations for the 

 student. Occasionally, students with sufficient musical equip- 

 ment are encouraged to use musical scale symbols also. Any other 

 system which the student finds practicable for describing pitch 

 variations is encouraged. It is of course pointed out that birds 

 do not sing according to the musical scale and that musical scale 

 records are only approximate at best, especially because of varia- 

 bility in vocal performances. 



Under complexity, are included some of the most important 

 characteristics of bird voice. Is the vocal performance a single 



