By cage birds, I mean those kept by amateurs, for amusement, in their
apartments, generally selected for sweetness of song or beauty of
plumage; but the naturalist has other reasons for surrounding himself
with these pleasing creatures: they enliven him, and he delights in
studying their habits and characters. To attain these objects it is
necessary, in the first place, to be able to distinguish readily between
the males and females, since the former are generally superior in their
powers of song, and therefore preferable. I have, for this reason, made
a point, in the following sketch of the history of house birds, of
showing the colours and other marks which characterise the two sexes;
and, as all birds cannot be tamed, whilst many others offer no
inducement to make the attempt, it follows that those about to be spoken
of must necessarily be but a small proportion of all the known species
of birds.