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 reared 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 has given rise to the 
theory of the mimetic origin of bird song, and which 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 Hawk, coo 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 
