3 

 nomenon as hatred ; they are either manifestatious of fear, a much sim- 

 pler form, of m.eutal activity, oiLar e al arm-cries, uttered for the purpose of 

 calling others to the rescue ; that is, they are dependent on a rudimentary 

 reasoning faculty, which is but a slight advance on instinct and grovrs out 

 of it. That a fixed animosity does not exist in birds is plainly shovrn by 

 the fact that species hostile to small birds during the breeding season on- 

 ly, such as Crows and Jays, dwell with them in comparative peace during 

 the rest of the year, however great the aversion manifested while the 

 eggs and young are in the nest. Raptorial birds are of course always re- 

 garded as natural enemies, but. Judging from the analogy of the former 

 case, it seems probable that they are only held in fear which has grown 

 instinctive. 



From the facts above given, and from many others of a like nature that 

 might easily pe presented, it seems hardly reasonable to suppose that the 

 songs of birds have any more psychical significance than many other phe- 

 nomena which they manifest. As before indicated it is easy to imagine 

 that the endless variety of notes which they produce might be, judged by 

 a human standard, expressive of an indefinite number of moods of mind. 

 It seems, however, to be a general law among vertebrates, excluding man, 

 that the vocal powers are developed, not according to the position occu- 

 pied in the whole series, but according to the mean degree of physical ac- 

 tivity attained. Though there are exceptions to this, they are not suffi- 

 ciently numerous to destroy its force as a law. Birds are by far the most 

 active of all vertebrates. Metabolism and catabolism reach in them their 

 climax, the bodily temperature is higher than in any other class ; the vital 

 functions are performed with greater rapidity, and hence the vocal pow- 

 ers reach a higher stage of development. The same law holds within the 

 class as in the whole vertebrate division. For example, the Vultures and 

 Herons, which are comparatively sluggish, have very^limited voice powers 

 or none, while the Sparrow and Finch family, which are among the most 

 active of birds, are unsurpassed in the gift of song. 



The subject will doubtless admit of infinite research, and presents op- 

 portunities for many interesting discoveries. I have here presented, but 

 in a very brief and general way what seems to me the most natural, an^ 

 iu fact the only reasonable theory regarding it. 





