when they were moulting, "does it hurt birds to lose their feathers,
uncle?"

"It is probably not as comfortable as being nicely dressed, and
sometimes they seem quite miserable, especially if they shed old
feathers faster than new ones can grow to replace the lost ones. Some
birds, like Ducks, lose their wing-feathers all at once, and cannot fly
for quite a while. But Heart of Nature is kind to his children, as a
rule. Most birds shed their rowing feathers one at a time in each wing,
so that they never lose their power of flight. Now this will do for
wings, tails, and feathers. Come! what is the next thing you notice
about this Sparrow? Is it entirely covered with feathers?"

"Of course it isn't," said Dodo; "it hasn't any feathers on its beak or
on its feet, else how could it eat and hop about?"

"That is right. These parts of a Sparrow are bare; they never have any
feathers; and the skin on them is hard and horny, as different from soft
thin skin as finger-nails. Now look at the beak, and think how many
things a Sparrow has to do with it. He has no hands or paws, and so he
must pick up everything he eats with his beak. He has no teeth, and so
he must bite his food with his beak. He feeds on seeds like a Canary
bird; so his beak comes to a sharp point, because seeds are small things
to pick up; and it is very strong and horny, because seeds are hard to
crack, to get at the kernel. Notice, too, children, that his beak is in
two halves, an upper half and a lower half; when these halves are held
apart his mouth is open, so that you can see the tongue inside; and when
the two halves are closed together the mouth is shut. These halves are
called the _upper mandible_ and the _lower mandible_."