MOTIF OF BIRD SONG. 79 



life, that the earth holds, man not excepted ? 

 I do not undertake to answer my interroga- 

 tory directly ; but to me it is significant in 

 this connection that of all the hundreds— nay, 

 thousands— of wild-birds that I have killed, 

 and have seen killed, and of all that I have 

 dissected for one purpose or other, I have 

 never found one that was diseased, so far as 

 I could discover, save from wounds, unless 

 the presence of intestinal worms in a perfectly 

 strong and healthy appearing subject may 

 have indicated disease. I have dissected and 

 minutely examined the mouth, throat, larynx, 

 syrinx, and lungs of a great number of song 

 birds, and in every case those organs have 

 been in a perfectly normal and healthy state, 

 so far as I could by any means discover. 



Among human beings a fine voice is the 

 notable exception ; among male mocking- 

 birds in a wild state there is no exception — 

 they all sing, and so nearly equally well that 

 it requires close attention to discover any dif- 

 ference. So one wild bluebird's piping is 

 practically identical, in volume, compass, and 

 timbre, with that of every other wild male 

 bluebird in the world. From this and a hun- 

 dred kindred facts, it is safe to say that gene- 

 ration and the constant transmission of or- 

 ganic power and equipoise are very nearly 

 perfect with birds of the highest order. In- 

 deed, in song, as in so many other ways, the 

 bird shows the operation of a nearly unerring 

 heredity, and I have been forced to conclude, 

 from all that I have been able to note in the 

 lives and habits of song-birds, that a good 

 part of bird-song is the mechanical response 

 to what may be called hereditary memory. 

 The mocking-bird, reared in captivity, far 

 from the haunts of its ancestors, will repeat 



