Why is this the answer?

The answer is snow because this lovely riddle uses beautiful word pictures to describe tiny, icy flakes that float gently down from the clouds. The riddle acts like a secret code, and we can crack it by looking at each line carefully. The first line says, "White bird, featherless, flying out of paradise." When you look at snow, you see a brilliant, bright white color, just like a white bird. However, snow is made of tiny ice crystals, so it is "featherless" because it is not a real bird. It flies, or floats, on the air from its home high up in the sky, which the riddle calls "paradise." The big, gray clouds are where the snow starts before it drifts down to the ground to cover the world in white. Next, the riddle mentions "Flying over sea and land." This shows us how far and wide the snow can travel. Snow does not only fall in your town or on your backyard; the wind carries it across vast areas, covering both dry land and the enormous ocean. It is a natural traveler that can be seen all over the world where the weather is cold enough. The tiny white specks are carried by the wind and drift gently downward, settling on everything below, which is why it flies over both the sea and the land. The final and most important clue is "Dying in my hand." This clue asks you to imagine catching a snowflake. When you put out your bare hand, the snowflake lands on your warm skin. Since a snowflake is made of frozen water, your body heat causes it to melt instantly. It changes from a pretty, six-sided crystal into a tiny drop of water. In the riddle's imaginative language, this quick melting is described as "dying" or disappearing. All of these wonderful clues about being white, flying everywhere, and melting when you hold it point perfectly to one amazing thing: snow. It is one of nature's most beautiful and delicate creations.