70 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



form of a pure High Trill may be essentially similar to that of a pure 

 Squeak, only on a much longer time scale. The sequence of rises and 

 falls in pitch within a single short Scream may be equally similar to 

 the arrangement of the corresponding features within both a single 

 Squeak and a single High Trill. 



Fig. 18. — A series of four notes uttered by an immature. 



Based upon a spectrogram by a "Sona-graph." 

 This series sounded, to me, like one "pure" Squeak followed immediately by 

 a short High Trill. As a whole, it is comparable to the series shown in figure 15, 

 which sounded as if it were composed of four separate Squeaks. 



Therefore, although most High Trills appear to be, or sound as if 

 they were, accelerated series of several Squeaks, the same morpho- 

 logical effect might be produced by slowing down a single Squeak in 

 such a way that the individual components within it become more dis- 

 tinct and widely separated from one another. Similarly, the effect of 

 a short Scream could be produced either by slowing down and length- 

 ening a single Squeak, while maintaining or strengthening the con- 

 nections between its components, or by letting a series of several 

 Squeaks "run together." In other words, many or most High Trills 

 could be interpreted as discontinuous series of either Squeaks or com- 

 ponents of Squeaks, while many or most short Screams could be 



