SUGGESTIONS FOR THE STUDENT 65 



within sound of whose voices they have been reared. There are, for 

 example, a number of cases in which young House or English Sparrows 

 when reaped with Canaries have learned the Canary's song. Two 

 Baltimore Orioles, reared by W. E. D. Scott ('04) apart from all other 

 birds, developed a song of their own which was wholly unlike that of 

 their species, and this song was learned by four other Baltimore Orioles 

 which were subsequently reared in the companionship of the first two. 



It is this strong tendency to imitate which Jias given rise to the 

 theory of the mimetic origin of bird song, and wmch is no doubt largely 

 responsible for much of the individual variation so prevalent in birds' 

 songs. There is, for example, a Maryland Yellow-throat now (May, 

 1910) living near my home, the first half of whose song is that of the 

 Yellow Warbler, while the remainder resembles that of its own species, 

 evidence that the inherent predisposition toward the acquisition of the 

 song of its ancestors was not sufficiently strong to prevent its song from 

 being modified by the notes of another species. 



It would be interesting to determine just when this presumably 

 inherent tendency is active. Is the nestling unconsciously influenced by 

 the song of its parent during the period of its infancy? Single-brooded 

 birds may not hear the song of their species from the time they leave 

 the nest until the following spring song again announces the opening 

 of the nesting-season. It seems probable, therefore, that their song is 

 acquired during the formative period of immaturity and before they 

 come into contact with other species whose notes their strong mimetic 

 gifts might lead them to adopt as their own, as doubtless did the Mary- 

 land Yellow-throat mentioned above. 



With some species the tendency to imitate is functional long after 

 it has served its universal purpose of giving them the notes character- 

 istic of their species. Among our birds the Mockingbird takes first 

 rank as a mimic, and L. M. Loomis tells me of one with a repertoire 

 containing no less than thirty-two songs of other species of birds; but 

 on the other hand some Mockingbirds sing only their own song. The 

 Catbird, White-eyed Vireo, Blue Jay and introduced Starling are also 

 to be numbered among the mimics. 



SUGGESTIONS FOR THE STUDENT 



What North American birds are voiceless? Which possess rudimentary 

 voices? Trace the development of voice. Define the difference between 

 call-notes and song. Note the development of call-notes in the young of 

 prsecocial birds; of altricial birds. Interpret, as far as possible, the call-notes 

 of certain species. Give illustrations of different types of anger calls (e. g. 

 spitting of brooding Chickadee, snapping of bill by Screech Owl, hiss of 

 Duck, etc.); of alarm notes; of scolding notes. How are call-notes used 

 by migrating birds? Do birds understand the call-notes of other than their 

 own species? Do the young understand the notes of their parents? What 

 relation exists between voice and character (e. g. scream of Hawkpcoo of 

 Dove)? Define Oscines. Give instances of song in non-Oscines; in the 

 female. Define the song season. What species have been heard singing in 

 the fall or winter? What is the relation between song and the advance of 



