Birds are the only animals that have feathers. Feathers are the coat a bird wears on its body，just like the hair most of other kinds of animals wear on their bodies. We，human beings，don't depend on feathers or hair to keep us warm，as birds and animals do，we have our clothes. The feathers and shapes of the birds help us to tell one kind from another. Feathers come in beautiful colors.
Many birds use colors to hide from enemies（敌人）. This is called camouflage. All birds molt（换毛），but the ptarmigan molts twice a year，changing color to go right for the season. In winter，when snow is on the ground，it has white feathers. In spring，it molts and grows brown feathers that match up with the land，grass，trees or other conditions where it lives. When winter comes，it molts again and grows white feathers.
Besides feathers，birds can have good voices and are good at singing. Many birds，such as the robin，sing to send messages to other birds. Each type of songbird has its own song. By singing，birds show who they are and where their land is. In spring，many birds sing together loudly at daybreak. The sound they make is known as the dawn chorus，so﹣called"early morning singing of love" by many people in a Chinese yet simpler way.
It refers to .
It molts a year.
Because they show and where their land is by singing.
At daybreak in .
It gives us some basic of birds.
