360 APPENDIX. VI. 



song of the linnet, nor that a nightingale or par- 

 tridge could be taught to speak. 



And here it may not be improper to explain 

 what I mean by birds learning to imitate the 

 notes of others, or the human speech. 



If the birds differ little in shape or size (par- 

 . ' . ticularly of the beak*) the imitation is com- 

 monly so strong that 



" Mire sagaces falleret hospites 



" Discrimen obscurum." Horat. 



* It seems very obvious why the form and size of the beak 

 may be material ; but I liave also observed, that the colour of a 

 bird's bill changes, when in or out of song ; and I am informed, 

 that a cock seldom crows much, but when his comb is red. 



When most of the finch tribe are coming into song, there is 

 such a gradual change in the colour of their bill ; thus, those of 

 the chaffinch and linnet are then of a very deep blue, which 

 fades away again, when the bird ceases to be in song. 



This particular should be attended to by the ornithologist, in 



his description ; because, otherwise, he supposes the colour of the 



, bill to be permanent, which is by no means so. 



^ This alteration, however, rather seems to be the symptom 



than the cause of a bird's coming into song, or otherwise, and I 



have never attended to this circumstance in the soft billed birds 



' sufficiently, to say whether it holds also with regard to them. 



A very intelligent bird-catcher, howe\'er, was able to prognos- 

 ticate, for three winters together, when a nightingale, which I 

 kept so long, was coming into song (.though there was no change 

 in the colour of the bill), by the dung's being intermixed with 

 large bloody spots, which before was only of a dead white. 



This same bird-catcher was also very successful in his pre- 

 scriptions for sick birds, with regard to the ingredients of which 

 he was indeed very mysterious. 



He said, that as he could not feel their pulse, the circum- 



