Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

236 A THEORY OF BIRDS' NESTS.
peculiarity of structure which is hereditary; as when
the descendants of tumbler pigeons tumble, and the
descendants of pouter pigeons pout. In the present
case, however, I compare it strictly to the hereditary,
or more properly, persistent or imitative, habits of
savages, in building their houses as their fathers did.
Imitation is a lower faculty than invention. Children
and savages imitate before they originate; birds, as
well as all other animals, do the same.
The preceding observations are intended to show,
that the exact mode of nidification of each species of
bird is probably the result of a variety of causes, which
have been continually inducing changes in accordance
with changed organic or physical conditions. The
most important of these causes seem to be, in the first
place, the structure of the species, and, in the second,
its environment or conditions of existence. Now we
know, that every one of the characters or conditions
included under these two heads is variable. We have
seen that, on the large scale, the main features of the
nest built by each group of birds, bears a relation to
the organic structure of that group, and we have,
therefore, a right to infer, that as structure varies, the
nest will vary also in some particular corresponding
to the changes of structure. We have seen also, that
birds change the position, the form, and the construction of their nest, whenever the available materials or the available situations, vary naturally or
have been altered by man; and we have, therefore,
a right to infer that similar changes have taken place,