106 NATURAL SELECTION v 
render it certain that the peculiar notes of birds are acquired 
by imitation, as surely as a child learns English or French, 
not by instinct, but by hearing the language spoken by its 
parents. 
It is especially worthy of remark that, for young birds to 
acquire a new song correctly, they must be taken out of 
hearing of their parents very soon, for in the first three or 
four days they have already acquired some knowledge of the 
parent notes, which they will afterwards imitate. This shows 
that very young birds can both hear and remember, and it 
would be very extraordinary if, after they could see, they 
could neither observe nor recollect, and could live for days 
and weeks in a nest and know nothing of its materials and 
the manner of its construction. During the time they are 
learning to fly and return often to the nest, they must be able 
to examine it inside and out in every detail, and as we have 
seen that their daily search for food invariably leads them 
among the materials of which it is constructed, and among 
places similar to that in which it is placed, is it so very 
wonderful that when they want one themselves they should 
make one like it? How else, in fact, should they make it? 
Would it not be much more remarkable if they went out of 
their way to get materials quite different from those used in 
the parent nest, if they arranged them in a way they had seen 
no example of, and formed the whole structure differently 
from that in which they themselves were reared, and which 
we may fairly presume is that which their whole organisation 
is best adapted to put together with celerity and ease? It 
has, however, been objected that observation, imitation, or 
memory can have nothing to do with a bird’s architectural 
powers, because the young birds, which in England are born 
in May or June, will proceed in the following April or May 
to build a nest as perfect and as beautiful as that in which it 
was hatched, although it could never have seen one built. 
But surely the young birds before they left the nest had 
ample opportunities of observing its form, its size, its position, 
the materials of which it was constructed, and the manner in 
which those materials were arranged. Memory would retain 
these observations till the following spring, when the materials 
would come in their way during their daily search for food, 
