[ 2 7 6 1 
that a fparrow would not imitate the fong of the 
linnet, nor that a nightingale or partridge could be 
taught to fpeak. 
And here it may not be improper to explain what 
I mean by birds learning to imitate the notes of 
others, or the human fpeech. 
If the birds differ little in fhape or fize (particularly 
of the beak *), the imitation is commonly fo ftrong, 
that 
* It feems very obvious why the form and fize of the beak may 
be material ; but I have alfo obferved, that the colour of a bird’s 
bill changes, when in or out of fong; and I am informed that 
a cock feldom crows much, but when his comb is red. 
When moft of the finch tribe are coming into fong, there is 
fuch a gradual change in the colour of their bill ; thus, thofe of 
the chaffinch and linnet are then of a very deep blue, which 
fades away again, when the bird ceafes to be in fong. 
This particular fhould be attended to by the ornithologifl, in 
his defcription ; becaufe otherwife he fuppofes the colour of the 
bill to be permanent, which is by no means fo. 
This alteration, however, rather feems to be the fytnptom 
than the caufe of a bird’s coming into fong, or otherwife, and I 
have never attended to this circumftance in the foft billed birds 
fufficiently, to fay whether it holds alfo with regard to them. 
A very intelligent bird-catcher, however, was able to prog- 
nofticate, for three winters together, when a nightingale, which 
I kept fo long, was coming into fong (though there was no 
change in the colour of the bill), by the dung’s being intermixed 
with large bloody fpots, which before was only of a dead white. 
This fame bird-catcher was alfo very fuccetsful in his prefcrip- 
tions for fick birds, with regard to the ingredients of which he 
was indeed very myfterious. 
He faid, that as he could not feel their pulfe* the circum- 
ftances which he chiefly attended to were their weight, as well 
as both the confidence and colour of their dung. 
He always frankly faid what he expeHed from his prefcrip- 
tions, and that if fuch and fuch changes did not foon take place, 
« Mire 
