64 'Journal of Comparative Neurology and Psychology. 



of three notes, and gradually this trisyllable comes to have exactly 

 the accent, the tone-quality, and the melody of the adult coo. But 

 even after attaining the trisyllabic form the early coo has three 

 definite differences from the adult utterance, as follows: 



First. The different notes of the coo are separated more in the 

 young than in the adult, often allowing a considerable rest between. 

 This fact, together with the general character of the utterance, gives 

 the impression that the young bird coos with difficulty and at the 

 expense of considerable effort. 



Second. The rolling sound, represented by the letter r, is absent 

 from the earliest coos, and develops rather slowly, for even when it 

 does first appear it is a perfunctory performance. 



Third. The appendix to the coo, represented by the syllables "(/o 0," 

 is not given until the age of three or four months, and when it is 

 first given it is only a monosyllable. 



In addition to the three features enumerated, the juvenile coo is 

 characterized by poverty in the quality of sound and a hurriedness 

 and lack of all beauty in the inflection. As the bird grows older, 

 the coo becomes loud, voluminous, and mellow, and acquires a grace- 

 ful, gliding inflection, which, without changing the general form of 

 the melody, gives it an entirely new and improved character. 



The perch-coo and the bowing-coo develop at an equal rate and 

 become practically of the adult form at the age of about seventeen 

 weeks. But at this age the nest-call coo is still decidedly imperfect 

 (at least in the male). All through the development of voice the 

 nest-call lags behind the other coos. This is perhaps because the nest- 

 call is purely a sexual expression, whereas the other two forms of 

 coo are used to express emotions which may be developed before 

 sexual maturity, such as combativeness, or simple good-spirits. 



Influence of old birds. — Pigeons, young and old, are extremely 

 sensitive to suggestion. The young ones often give a certain note 

 when they hear the parents give it; this is noticed as soon as the first 

 of the adult cries appears, i. e., the alarm-note. The more the young 

 hear other birds, the more they call. Thus the calling of other birds 

 may lead the young to give a certain sound earlier than they would 

 give it if left alone. But the young do not imitate the adults, in 



