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 eed 
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 
«« Miré sagaces falleret hospites 
«¢ Discrimen obscurum.” = Horart, 
* Tt seems very obvious why the form and size of the beak 
may be material; but I have 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, however, 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- 
