“Keep out or I'll chase you out! This is my property!” You hear this every spring. It is a long musical sound —a bird song! Birds use their songs to communicate different messages to one another. People who study bird sounds are learning their meanings.

    Usually it is the male that sings. Early in spring he sings to say that he has picked out a piece of property. He sings to attract a female of his same kind. Together they will raise a family in his territory (领地). He sings to tell all other birds of his kind to keep out.

    Each kind of bird has its own type of song. Cardinals sing something that sounds a little like “What cheer, cheer, cheer.” Towhees sing, “Drink your tea.”

    Most of the time, birds pay attention only to the songs of birds of their own kind. Cardinals answer cardinals, and song sparrows answer song sparrows. A cardinal knows that a song sparrow will not try to steal its mate. So you can see one reason why a cardinal may chase away another cardinal but will not bother a song sparrow.

    Most different kinds of birds eat different things. To find enough to eat, a bird needs a big piece of land to search in. Many kinds of birds have some ways of dividing up the land into territories. Song sparrows, cardinals ovenbirds, and white-throated sparrows are some of the birds that have territorial systems.

    Especially in early spring, birds work out the boundaries between their territories by singing “keep out” threats and by chasing and fighting each other. The birds continue singing to tell females that they have set up territories. Neighboring birds seem to agree that there are make believe fences between their pieces of property. Then they do not have to waste energy chasing each other instead of taking care of their young.

    Scientists guessed that some birds could recognize their neighbors by small differences in their songs. Two scientists who studied white-throated sparrows found that these birds can even tell the difference between songs of individual birds of their own kind. White-throated sparrows have songs that seem to say “I'm your neighbor” or “I'm a stranger” or “I'm your neighbor to the west.” Other kinds of birds could tell neighbors from strangers by their songs, too.

    The advice offered from any other 82-year-olds might have made young people yawn and roll their eyes. But when former South African president Nelson Mandela advised two dozen local youth leaders in Los Angeles to take education seriously, his audience was listening.

    The famed old man said to the young people that if they expected to improve the lives of others in the future, they must work at improving their own lives now. "Education is one of the most important weapons you have,” Mandela advised. “It will place you in a far better position to serve yourself and your community.”

“The point is, he was young once and rebellious(叛逆的)once and he kept his dream alive, just as you each have dreams,” explained South Africa's ambassador to the United States, Sheila Sisulu, as she introduced Mandela to the young crowd.

    Asked for specific advice about changing society by 21-year-old Ahmed Younis, Mandela suggested that somehow helping arouse more American interest in foreign affairs might be a start.

There is an impression that Americans, in general, have not followed international developments properly, Mandela said. “I'm not making that statement myself, but there are serious political analysts who say Americans are not well informed as to what has happened in the world.”

22-year-old Omari Trice said Mandela left him full of enthusiasm. “ He's a person who set the tone for an entire nation, said Trice. “You come away feeling you need to be a superman in order to get things done.”

    Worldwide, the most people willing to return your mobile phone if you've lost it are to be found in Slovenia, and the fewest in Malaysia. This finding is the result of an interesting study in 32 of the world's largest cities. Altogether, researchers 'lost' 960 new mobile phones. They got back 654 of them，or 68 percent. Prague came in at number eight. There, 23 out of 30 people who were willing to return the mobile phone.

    It wasn't a traditional study. Two researchers carefully chose different places such as areas with high crime(犯罪)and busy downtown shopping areas, to “lose” the phones. When one of the researchers dropped a phone, the other would keep watching from a distance. The honest finders tried their best to find the owner with the help of the address book in the phone. They were told why the study was done and asked why they acted the way they did.

    It was found that the busier the place where the researchers dropped the phone, the greater the chance of it being returned. Another interesting finding was that women were generally more likely than men to return the phone. Researchers also found that most people still have a sense of honesty. “Crime is simply not good behavior (行为), ”said an expert. “People want to trust others, and want to be trusted.”

    In recent decades, social isolation has been recognized as a major risk to our health and long life. It's twice as bad for you as being overweight and nearly as bad as smoking. The rising number of people who say they are affected, across a wide range of ages, is shocking. In reality, you can suffer the ill effects of loneliness even if you are not socially isolated.

Comedian Robin Williams made a striking observation in 2014: "I used to think the worst thing in life was to end up all alone. It's not. The worst thing in life is to end up with people who make you feel all alone." Tracking large groups over time indicates that perceived（感知的）social isolation carries its own risk for morbidity（发病率）and mortality.

    The perception of isolation—from others of being in the social aspect-is not only a cause of unhappiness, it also signals danger. Fish have evolved to swim to the middle of their group when predators（捕食者）approach, mice housed in social isolation show sleep disruptions and reduced slow-wave sleep and prairie voles（田鼠）isolated from their partners then placed in an open field explore their surroundings less and concentrate on avoiding predators.

    These behaviours reflect an increased emphasis on self-preservation in the social aspect. For instance, fish on the edge of a school are more likely to be attacked by predators because they are easier to isolate and prey upon. Such observations reflect a more general principle that perceived social isolation in social animals activates neural（神经系统的）, neuroendocrine（神经内分泌的）and behavioural responses that promote short-term self-preservation. However, these responses bring a cost for long-term health and well-being.

    The range of harmful neural and behavioural effects of perceived isolation documented in adults include increased anxiety, hostility and social withdrawal; fragmented sleep and daytime tiredness; increased vascular resistance and changed gene expression and immunity; decreased impulse control; increased negativity and depressive symptoms; and increased age-related cognitive decline.

    Sadly, to date, attempts to reduce loneliness have met with limited success. A series of randomized controlled trials showed that they had only a small effect. Among the four types of interventions（介入）examined, talking therapy that focused on inappropriate thought processes had the largest impact. Social skills training, social support and increased opportunities for social contact were much less effective.

    Phil White has just returned from an 18,000-mile, around-the-world bicycle trip. White had two reasons for making this epic journey. First of all, he wanted to use the trip to raise money for charity, which he did. He raised ＄70,000 for the British charity, Oxfam. White's second reason for making the trip was to break the world record and become the fastest person to cycle around the world. He is still waiting to find out if he has broken the record or not.

    White set off from Trafalgar Square, in London, on 19th June 2004 and was back 299 days later. He spent more than l,300 hours in the saddle(车座)and destroyed four sets of tyres and three bike chains. He had the adventure of his life crossing Europe, the Middle East, India, Asia, Australia, New Zealand and the Americas. Amazingly, he did all of this with absolutely no support team. No jeep carrying food, water and medicine. No doctor. Nothing! Just a bike and a very, very long road.

    The journey was lonely and desperate at times. He also had to fight his way across deserts, through jungles and over mountains. He cycled through heavy rains and temperatures of up to 45 degrees, all to help people in need. There were other dangers along the road. In Iran, he was chased by armed robbers and was lucky to escape with his life and the little money he had. The worst thing that happened to him was having to cycle into a headwind on a road that crosses the south of Australia. For 1, 000 kilometres he battled against the wind that was constantly pushing him. This part of the trip was slow, hard work and depressing, but he made it in the end. Now Mr. White is back and intends to write a book about his adventures.

    In 2013, Gabby Frost founded Buddy Project when she was 15. At that time her best friend had been diagnosed(诊断)with a mental health condition, and that was the first time she was made aware of what mental illness was. She wanted to learn more and develop a good support system for her.

    Mental illness affects tens of millions of people in the United States each year, yet only half receive treatment, according to the National Institutes of Mental Health. Buddy Project's website says the service is not a substitute for therapy( 治疗)or other types of mental health care, and it directs people to resources for further help.

    Since founding the organization as a high school student, Frost has helped more than 200, 000 participants find a new friend. On the day when Buddy Project was launched, she used her powerful social media presence to attract nearly 3, 000 participants. "This was around the time when teens really began talking about mental health and found a supportive community online to talk about it,"she said.

    One of the biggest social barriers she had to jump over was that people didn't view her seriously because she was a 15-year-old girl, and even now, she's still a young woman. "Sometimes it's frustrating because people don't think what I do is needed or they don't think I'm professional" she said. "Most people are blown away that a 20-year-old girl is running this and that it's one person doing this but not a whole team. I'm just lucky that I've found a support system that has been able to help my mom and me with the project.