“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.

    How often do you let other people like a bad driver, a rude waiter, or an angry boss, change your mood?

    Sixteen years ago I learned a lesson. I got in a taxi, and we took off for Grand Central Station. We were driving in the right lane when all of a sudden, a black car jumped out of a parking space right in front of us. My taxi driver used his brakes, the tires made a loud noise, and at the very last moment our car stopped just 3cm from the back of the other car.

    I couldn't believe it. But then I couldn't believe what happened next. The driver of the other car, the guy who almost caused a big accident, turned his head around and he started shouting at us. I couldn't believe it!

    My taxi driver just smiled and waved at the guy. So, I said, “Why did you just do that? This guy could have killed us!” And this is when my taxi driver told me what I now call, “The Law of the Garbage Truck”. He said, “Many people are like garbage trucks. They run around full of garbage, full of anger and disappointment. As their garbage piles up, they look for a place to dump it. And if you let them, they'll dump it on you.”

    So I started thinking how often I let Garbage Trucks run right over me and how often I take their garbage and spread it to other people.

    I began to see Garbage Trucks. I see the load people are carrying. I see them coming to dump it. And like my taxi driver, I don't take it personally. I just smile, wave, wish them well, and move on.

    In many parts of the world, there are four seasons: spring, summer, fall and winter. In the U.S., there are only three: football, basketball and baseball. If you want to know what season it is, just have a look at what people are playing.

    For many people in the U.S., sports are not just for fun. They're almost a religion. Thousands of sports fans buy expensive tickets to watch their favourite teams and athletes play in person. Other fans watch the games at home. The most devoted sports buffs never miss a game. Many a wife becomes a “sports widow (寡妇)” during her husband's favorite season.

    America's devotion to athletics has created a new class of wealthy people: professional athletes. Sports stars often receive million -dollar salaries. Some even make big money appearing in advertisements for soft drinks, shoes and even toiletries (化妆品).

    Sports are an important part of Americans' culture. Throughout their school life, Americans learn to play many sports. All students take physical education classes in school. Some try out for the school teams, while others join school sports leagues. Athletic events at universities attract scores of fans and benefit the whole community.

    It's common knowledge that sleep problems can be caused by things such as stress, anxiety, or even using a smartphone before bedtime. But recently, a team of researchers discovered that genes could also be a cause of sleepless nights.

    The scientists, from Rockefeller University in New York, US, found that delayed sleep phase disorder（DSPD，睡眠相位后移综合症）, a condition that affects one's sleeping patterns, is passed down via a mutated（突变的）gene. DSPD sufferers wake up later and go to bed later than the average person. To come to their conclusion, the team studied a 46-year-old woman who is only usually able to fall asleep at 2 or 3 in the morning. It was discovered that the woman's body produces the hormone that helps her sleep at night up to 7 hours later than regular sleepers. The scientists found this was caused by a mutation in one of the woman's genes, one that helps regulate the “body clock”.

    Some of the woman's family members were also found to share the same mutation—and the same sleeping problems –leading the scientists to believe that sleep troubles are passed down through the generations.

    However, having this mutation doesn't mean you automatically have sleep problems. The team also found two people who had the mutation but reported no problems with their sleep.

    But while this is an interesting discovery, it offers no help to those who can't fall asleep at night—although there are a few things you could try to help you sleep earlier.

    BBC journalist Michael Mosley produced a TV documentary in May in which he talked about his battle with insomnia（失眠）and the techniques he used. “I avoid social media for at least an hour before bed, I do mindfulness exercises, and if I wake up in the middle of the night, I read a book for an hour or so,” he wrote in an article for the Radio Times.

    Chocolate could soon be a thing of the past, after scientists warned that the cacao plant, from which chocolate is made, could be extinct within 32 years.

    Over half of the world's chocolate comes from just two countries in West Africa­Cote d'Ivoire and Ghana­where the temperature, rain, and humidity provide the perfect conditions for cacao to grow. But the threat of rising temperatures over the next three decades caused by climate change, is expected to result in a loss of water from the ground, which scientists say could upset this balance.

    According to the related data, a temperature rise of just 2.1℃ could spell an end for the chocolate industry worldwide by 2050. Farmers in the region are already considering moving cacao production areas thousands of feet uphill into mountainous area­much of which is currently preserved for wildlife. But a move of this scale could destroy ecosystems that are already under threat from illegal farming and deforestation.

    Part of the problem, according to Doug Hawkins, is that cacao farming methods have not changed for hundreds of years. "Unlike other tree crops that have benefited from the development of modern, high yielding strains and crop management techniques to realize their genetic potential, more than 90% of the global cocoa crop is produced by small farms with unimproved planting material," he said. "It means that we could be facing a chocolate decrease of 100,000 tons a year in the next few years."

    Now scientists at the University of California at Berkeley have teamed up with American candy company Mars to keep chocolate on the menu. Using the controversial(有争议的) gene-editing technology known as CRISPR they are trying to develop a type of the cacao plant capable of surviving in dryer, warmer climates. If the team's work on the cacao plant is successful, it could remove the need for farmers in West Africa to relocate to higher ground, and perhaps even allow cacao to be grown elsewhere in the world.

"Given that signs of Alzheimer's disease (老年痴呆症) start to accumulate in the brain several decades before the disease begins, understanding the connection between sleep and cognition (认知) earlier in life is critical for understanding the role of sleep problems as a risk factor for the disease," said study author Yue Leng, PhD, of the University of California, San Francisco.

The study involved 526 people with an average age of 40. They were followed for 11 years. Researchers looked at participants' sleep duration and quality. Participants wore a wrist activity monitor for three continuous days on two occasions approximately one year apart to calculate their averages. Participants slept for an average of six hours. Participants also reported bedtime and wake-up time in a sleep diary and completed a sleep quality survey with scores ranging from 0 to 21. A total of 239 people reported poor sleep with a score greater than five.

Researchers also looked at sleep fragmentation (碎片化), a measure of restlessness during the sleep period expressed as a percentage. The higher the value, the more sleep is interrupted. Participants were divided into three groups based on their sleep fragmentation score. Of the 175 people with the most interrupted sleep, 44 had poor cognitive performance 10 years later, compared to 10 of the 176 people with the least interrupted sleep.

After adjusting for age, sex, race, and education, people who had the most interrupted sleep had more than twice the possibility of having poor cognitive performance when compared to those with the least interrupted sleep. There was no difference in cognitive performance at midlife for those in the middle group compared to the group with the least interrupted sleep.

However, due to the small sample size, the researchers were unable to fully investigate potential race or sex differences. "More research is needed to assess the link between sleep disturbances and cognition at different life stages and to identify if critical life periods exist when sleep is more strongly associated with cognition," Leng said.