Is having a tail (尾巴) just for good looks? No, many animals can't live without their tails.

For a squirrel, its tail is used for many things. In summer, its tail is like an umbrella. On rainy days, the squirrel usually puts the end of its tail over its head. When winter comes, the tail can be used as a blanket (毯子) . If the squirrel falls from a tree, its tail can act as a cushion (垫子).

A porcupine (豪猪) can use its tail to protect itself. A porcupine has quills (刺) all over its body, and the tail’s quills are the longest and the strongest. So if a human or an animal comes near the porcupine, it will swing its tail back and forth.

A whitetail deer is a very common deer. If the deer raises its tail, it is telling other deer, “________”. When other deer see the raising tail, they will run away to a safe place.

An opossum(袋貂) is really talented. It has a very long, thick tail. The tail is like another hand, because it can help carry things so that its four hands are free to climb up the tree.

Why don’t human beings have tails? You did have, when you were inside of your mother. As you grew up, the tail got smaller and smaller. Your tail was nearly gone when you were born, because it is not as useful as an animal’s tail.

The spider monkey (蜘蛛猴) is a special kind of monkey and usually lives in the rain forest (森林). What does it look like? The spider monkey is small. Its body is 35—66 cm long. It has a small head. Its arms and legs are long and thin. Its tail (尾巴) is long and thin, too. Its arms, legs and tail make it look like a spider. That’s why the spider monkey gets its name.

The spider monkey’s tail is even longer than its body. Its tail is 60—92 cm long. Its tail is very strong. The spider monkey always uses its tail to hang (悬挂) on to the branches (树枝). Then it can move among trees.

Birdsong is powerful. It can calm and comfort people, bring joy and hope. It might even help with your homework. Birdsong is loudest in spring and summer, but you can enjoy its advantages all year round.

Birdsong is what we call the song of a bird. It sings to interest a partner or to protect its home. Although most birds make a sound, there is a group of birds called songbirds that are “expert singers”. These include blackbirds, nightingales (夜莺), robins (知更鸟) and so on.

Research has shown that birdsong can be good for us. Dr Eleanor Ratciffe, from the University of Surrey, found that some birdsong made people feel less stressed (压力), and many people say listening to birdsong for five minutes a day could lift their feelings in winter. Birdsong connects humans to nature, which can be good for both mind and body. One opinion is that before humans lived in cities and towns they spent more time in the wild. This developed a positive connection to birdsong, because if birds are singing, it usually means there are no dangers nearby. Another reason is that birdsong avoids background noise, which helps to draw people’s attention. Some say listening to birdsong while doing homework can help them think. “Birdsong can make us less stressed and improve our happiness,” Elaine Bradley, a famous animal expert, tells reporters. “It can be fantastic for our health.” You can hear birdsong in a city street, a park, or even indoors through a window. “Simply enjoy the different songs and understand the different tones (音调) and richness of sounds,” Bradley says. In autumn and winter, fewer birds will be singing outside than in spring, but you can still hear birds such as robins, sparrows and starlings (八哥). A great way to listen to birdsong in winter is online. You can listen to Spring’s Dawn Chorus (合唱), which sounds so beautiful.