ON THE NOTES OF BIRDS. 37 
From these and similar observations I have long 
been thoroughly convinced myself that the calls of 
birds, which seem to be the simplest expressions of 
their sensations, are natural, not acquired; and in 
order to determine whether this is the case with 
their songs also, which are generally much more 
complex, and, consequently, have the appearance of 
being more artificial, the followimg experiments were 
made. 
In the summer of 1822 I procured three young 
Greenfinches (a cock and two hens), which, as they 
did not see till the fourth day after they were taken 
from the nest, must then have been only two days 
old *, 
These birds were reared by hand, in a house situ- 
ated in the town of Manchester, where they had no 
opportunity of hearing the notes of any bird, except, 
perhaps, the occasional chirping of Sparrows ; never- 
theless they had all their appropriate calls, and the 
cock bird had the song peculiar to its species. 
It was hoped, at. the time, that this experiment 
would be considered sufficiently decisive ; but recol- 
lecting that some persons, for the sake of showing 
their ingenuity in raising objections, might say that 
these birds remembered the notes of their parents, 
which they imitated as soon as they had acquired 
* From numerous observations which I have made, it appears 
that young birds usually begin to sce about the sixth day after 
they are hatched. 
