a bird is not only its mouth, but its hand, or rather its two hands.
For, as its arms and hands are turned into wings, all it has to depend
upon, in economical and practical life, is its beak. The beak,
therefore, is at once its sword, its carpenter's tool-box, and its
dressing-case; partly also its musical instrument; all this besides its
function of seizing and preparing the food, in which functions alone it
has to be a trap, carving-knife, and teeth, all in one.

21. It is this need of the beak's being a mechanical tool which chiefly
regulates the form of a bird's face, as opposed to a four-footed
animal's. If the question of food were the only one, we might wonder
why there were not more four-footed creatures living on seeds than
there are; or why those that do--field-mice and the like--have not
beaks instead of teeth. But the fact is that a bird's beak is by no
means a perfect eating or food-seizing instrument. A squirrel is far
more dexterous with a nut than a cockatoo; and a dog manages a bone
incomparably better than an eagle. But the beak has to do so much more!
Pruning feathers, building nests, and the incessant discipline in
military arts, are all to be thought of, as much as feeding.

Soldiership, especially, is a much more imperious necessity among birds
than quadrupeds. Neither lions nor wolves habitually use claws or teeth
in contest with their own species; but birds, for their partners, their
nests, their hunting-grounds, and their personal dignity, are nearly
always in contention; their courage is unequaled by that of any other
race of animals capable of comprehending danger; and their pertinacity
and endurance have, in all ages, made them an example to the brave, and
an amusement to the base, among mankind.

22. Nevertheless, since as sword, as trowel, or as pocket-comb, the
beak of the bird has to be pointed, the collection of seeds may be
conveniently intrusted to this otherwise penetrative instrument, and
such food as can only be obtained by probing crevices, splitting open
fissures, or neatly and minutely picking things up, is allotted,
pre-eminently, to the bird species.

The food of the robin, as you know, is very miscellaneous. Linnaeus says
of the Swedish one, that it is "delectatus euonymi baccis,"--"delighted
with dogwood berries,"--the dogwood growing abundantly in Sweden, as
once in Forfarshire, where it grew, though only a bush usually in the
south, with trunks a foot or eighteen inch