INTRODUCTION. 27 



they remain so, during the winter, till they sepa- 

 rate in spring, for the important purposes of in- 

 cubation. 



The song of birds has occasioned considerable 

 difference of opinion amongst naturalists ; but we 

 believe it is now decided to be the language of 

 love and that of defiance : and in this opinion we 

 agree. Birds differ much with regard to the ex- 

 cellence of their song, (by which we here mean 

 their warble or musical notes,) both as to its 

 sweetness and its duration. The notes of soft-bill- 

 ed birds are finely-toned, mellow, and plaintive ; 

 — those of the hard-billed species are sprightly, 

 cheerful, and rapid. This difference proceeds 

 from the construction of the larynx, as a large 

 pipe of an organ produces a deeper and more mel- 

 low-toned note than a small pipe ; so the trachea 

 of the nightingale, which is wider than that of th6 

 canary, sends forth a deeper and more mellow- 

 toned note. Soft-billed birds, also, sing more fi-om 

 the lower part of the throat than the hard-billed 

 species. This, together with the greater width of 

 the larynx of the nightingale. and other soft-billed 

 warblers, fully accounts for their soft, round, mel- 

 low notes, compared with the shrill, sharp, and clear 

 notes of the canary and other hard-billed songsters. 



