Have you ever wondered why birds sing? Maybe you thought that they were just happy. After all, you probably sing or whistle(吹口哨) when you are happy.

    Some scientists believe that birds do sing some of time just because they are happy. However, they sing most of the time for a very different reason. Their singing is actually a warning to other birds to stay out of their territory.

    Do you know what a “territory” is? A territory is an area that an animal, usually the male, claims as its own. Only he and his family are welcome there. No other families of the same species(物种) are welcome. Your yard and house are your territory where only your family and friends are welcome. If a stranger should enter your territory and threaten you, you might shout. Probably this would be enough to frighten him away.

    If so, you have actually frightened the stranger away without having to fight him. A bird does the same thing. But he expects an outsider almost any time, especially at nesting(筑巢) season. So he is screaming all the time, whether he can see an outsider or not. This screaming is what we call a bird's song, and it is usually enough to keep an outsider away.

    Birds sing loudest in the spring when they are trying to attract a mate（配偶）and warn others not to enter the territory of theirs.

    You can see that birds have a language all their own. Most of it has something to do with attracting mates and setting up territories.

    A. High tech with traditional life at Green Bank.

    Over millions of years, penguins（企鹅）have developed a keen sense of where to find food. Once they're old enough, they set off from the shores on which they were hatched for the first time and swim long distances in search of tasty fish like anchovies and sardines. But they don't search directly for the fish themselves.

    For example, when young African penguins head out to sea, they look for areas with low surface temperatures and high chlorophyll(叶绿素) because those conditions signal the presence of phytoplankton（浮游植物）. And lots of phytoplankton means lots of plankton（浮游动物）, which in turn means lots of their favorite fish. Well, that's what it used to mean.

    Climate change plus overfishing have made the penguin feeding grounds a mirage(海市蜃楼). The habitat is indeed plankton-rich—but now it's fish-poor. Researchers call this an “ecological trap.”

    “It's a situation where you have a signal that previously pointed an animal towards good quality habitat. That habitat's been changed, usually by human pressures. The signal stays, but the quality in the environment deteriorates.”

    Richard Sherley, a zoologist at the University of Exeter and his team used satellite imaging to track the African penguins from eight sites along southern Africa. Historically, the birds benefited from tons of fish off the coasts of Angola, Namibia and western South Africa, but now they're going hungry.

    “I was really hoping we'd see them going east, and finding areas where the fish had moved to but it ends up being quite a sad story for the penguins.” said Richard.

    The researchers calculate that by falling into this ecological trap, African penguin populations on South Africa's Western Cape have declined by around 80 percent.

    Some research groups are exploring the idea of moving chicks to a place where they can't get trapped, like the Eastern Cape. But Sherley thinks that a longer-term solution means making and carrying out rules to create more sustainable(可持续的) fishing industry, something that he says needs public support.

    You get anxious if there's no wi-fi in the hotel or mobile phone signal up the mountain. You feel upset if your phone is getting low on power, and you secretly worry things will go wrong at work if you're not there. All these can be called “always on” stress caused by smart phone addiction.

    For some people, smart phones have liberated them from the nine-to-five work. Flexible working has given them more autonomy（自主权）in their working lives and enabled them to spend more time with their friends and families. For many others though, smart phones have become tyrants（暴君）in their pockets, never allowing them to turn them off, relax and recharge their batteries.

    Pittsburgh-based developer Kevin Holesh was worried about how much he was ignoring his family and friends in favour of his iPhone. So he developed an app — Moment — to monitor his usage. The app enables users to see how much time they're spending on the device and set up warnings if the usage limits are breached（突破）. “Moment's goal is to promote balance in your life,” his website explains. “Some time on your phone, some time off it enjoying your loving family and friends around you.”

    Dr. Christine Grant, an occupational（职业的）psychologist at Coventry University, said, “The effects of this 'always on' culture are that your mind is never resting, and you're not giving your body time to recover, so you're always stressed. And the more tired and stressed we get, the more mistakes we make. Physical and mental health can suffer.”

    And as the number of connected smart phones is increasing, so is the amount of data. This is leading to a sort of decision paralysis（瘫痪）and is creating more stress in the workplace because people have to receive a broader range of data and communications which are often difficult to manage. “It actually makes it more difficult to make decisions and many do less because they're controlled by it all and fell they can never escape the office,” said Dr. Christine Grant.

    Your next car might drive itself. After years of trials on city streets, driverless vehicles are now on the way. Last month, a driverless bus began carrying passengers through Lyon, France. Most in the automobile industry think self-driving vehicles will be on the road by 2020 or earlier.

    Driverless cars will first be huddled with human-driven cars. But the first places where they will become dominant（统治的）are highly populated urban areas. Many advanced cities are already reducing the role of human-driven cars. Driverless cars will quicken that process and will bring us enormous benefits.

    Driverless cars will reduce accidents by around 90 percent. That's big—the annual deaths on the world's roads are about 1.2 million a year. Pollution and carbon emissions will drop, because urban driverless cars will be electric.

    On the other hand, driverless cars will cause problems. Over the next 20 years, the mostly low-skilled men who now drive trucks, taxis and buses will see their jobs reduced. Traditional carmakers are especially scared. The cars of the future might be made by tech companies such as Apple, Baidu and Google. Imagine Germany, where automobile making is the largest industry.

    Dramatic changes are coming, and driverless cars could arrive by 2020. But governments have barely begun thinking about it. Only 6 percent of the biggest US cities have taken them into their long-term planning. A decade ago anyone hardly saw the Smartphone coming. Now what about the driverless cars?

Yoga (瑜伽) is a kind of sport. It is very popular around the world now. Everyone, young or old, men or women, can do yoga.

There are many reasons why people like yoga. First, yoga can build up your muscle. Your body will become stronger and more flexible. Second, yoga helps you get rid of stress. What's more, yoga can help your mind stay calm. To put it simply, the reason why so many people are falling in love with yoga is that they are discovering how wonderful it is for their mind, body and spirit.

Yoga began in India about 5,000 years ago. At that time, people wanted to be free, healthy and live a long life. As a result, this kind of exercise was born. The early yoga was part of the religion (宗教). It was usually taught one to one—one teacher and one student. Later, it was accepted by more people.

Yoga is an Indian word that means "to join together". There are three parts of yoga altogether: exercise, breathing and meditation (冥想). In the past, people paid more attention to the spirit. The idea behind the exercise was to join the mind, body and spirit as one.

With the development of the exercise, more and more people are doing yoga as a way of keeping healthy. Among them, office ladies enjoy doing yoga most. Yoga can give them peace, help them feel relaxed and have fewer worries and illnesses.

When I was three, my parents took me to have an operation in India, which stopped my eyesight from deteriorating(恶化). Several years later we moved to Pakistan, where I received 12 operations within one year and went completely blind. Later, I realized that the doctors used me as an experiment.

I met my husband when he came over from India to study. I wanted to go to India to marry him, but it was almost impossible to emigrate. I made a crazy plan to cross the borders of several countries to get to India. I was arrested in the first country I escaped to. Back in Pakistan, I lost my job and was asked to sign a "never-to-escape" promise. Instead, when I got home, I made a cup of coffee and decided to make a formal application for emigration. The chance was slim, and people who applied to go to India found it hard to find a job in Pakistan while they were waiting. In the end, my husband managed to smooth the way for my emigration. We got married and had children. But after nine years, he died of brain cancer. I was helpless for a while, and then I learned to face reality optimistically. He taught us happiness came from inside us.

Six years ago, I brought home a dog called Moritz from the seeing-eye dog centre. He was short with long ears. No one liked him because of his pathetic(可怜的)appearance. We were almost always together. Moritz could not leave me for even one minute. Now when I walk down the street, not like before, people will come up and say, "What a good seeing-eye dog! ", and have a little chat with me as a normal creature.

I'm now working for the Association of the Blind and I have many good friends, and a special friend in Hamburg. It is a wonderful feeling to speak freely with someone I can't see, to trust one another.