The Audubon Societies 



181 



the cry of 'wolf, wolf,' however, continued use of the 'squeak' at one spot 

 destroys its efficacy. 



Another call that is apparently recognized by more than one species, is 

 the food-call of the young, particularly the call that is developed when the 

 young leave the nest, so that their whereabouts will be known to the parents. 

 This call is very insistent with some young like those of the Cowbird and 

 Baltimore Oriole. The writer has observed a Redstart returning with food for 

 its young, to be waylaid by a young Cowbird that was being raised by a Red- 

 eyed Vireo, and to actually give the food which it carried to the young Cow- 

 bird, so insistent were its cries. Upon another occasion, where two Robins 

 were nesting side by side, unusual enough in itself, one of the Robins deserted 

 its own young, which were just hatched and had not yet developed the food- 

 call, to assist in the care of the 

 other young which were just leaving 

 the nest and whose cries were very 

 insistent. 



The calls of birds are apparently 

 inherited, for young birds hatched 

 in incubators or under other birds 

 seem to have the calls of their 

 species. Their songs, however, are 

 apparently largely a matter of 

 imitation, and birds never hearing 

 the songs of their species develop 

 very different songs. The adapta- 

 bility of birds' voices in this respect 

 varies considerably. Some birds like 

 the Parrots and members of the 

 Crow family, learn a variety of 

 sounds readily and are easily taught 

 to imitate the human voice. Other 

 birds can be taught to whistle tunes or the songs of different ;birds, and 

 birds like the Mockingbird, Catbird, and Brown Thrasher seem to do this 

 naturally and are well known as mimics. 



In the development of birds from their reptile-like ancestors, undoubtedly 

 the call-notes arose long before songs, for true songs are still confined to what 

 are considered the higher families of birds, i. e., those above the Flycatchers. 

 The lower orders of birds have substitutes for song, some of which are just as 

 elaborate as the songs of many of the Corvidae or Icteridae, which are considered 

 true singing birds. The laughing of the Loons, the cooing of the Grebes, the 

 whistling of the shore-birds, for example, are much more musical than the 

 guttural notes of the Crow or the shrill, hissing notes of the Cowbird. Nor 

 can one always determine the musical quality of the song by the elaborateness 



SWAMP SPARROW SINGING FROM A 

 FAVORITE REED 



