Why Can BIrds Fly in the Sky?

(Author's note: This is just pure fantasy. Do not believe a
single word of it.)

    Once upon a time, birds could not fly in the sky. They had
wings, but they could only walk or hop.

    One summer, it rained too much, all the birds climbed up to
trees. One pigeon thought sadly,'If I can fly in the sky, that
must be very good, then I can find another place to live.' The
pigeon told other birds this thought. All birds agreed except
the ostrich and the penguin. They said,'We cannot fly, we do not
need to overcome it. We should be satisfied with our own condition.'

    So, when the water had gone down from the land, the birds
learnt to fly. At last, a nightingale became the first bird
that mastered the skills, and, now became a teacher, she
demonstrated her achievement to others. But the ostrich and
penguin still refused to learn it.'We are happy with our own
selves now. It can be very dangerous for us to learn flying. We
may even die when something goes wrong,'they explained.

    Now, all the birds have developed their flying skills and
fly in the sky with leisure, with the exception of the ostrich
that runs on sand, while penguin walks on ice.