“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.

    I climbed Kilimanjaro with Lava Expeditions (探险队) during the rainy season.

    I flew to Nairobi in Kenya and spent several days there. At my hotel in Nairobi I met the rest of the group with whom I would spend the next week. We all travelled on the bus together for a 6-hour journey into Tanzania and then Arusha, a quiet town.

    After we arrived at our hotel in Arusha, we had dinner and a few drinks. Then we were introduced to more members including Taddeus Minja, the main guide, who was very experienced — climbing Kilimanjaro runs through the generations (代) of his family.

    The next day the Lava Expeditions members checked if we had the correct and enough clothing for our expedition on Kilimanjaro. Only one person needed to bring more clothes.

    After that we set off, walking in the rain through the beauty of the rainforest, all the way to the first camp. I was happy the next few days as the view was so wonderful and changed every day. I suffered a little during the trip and I felt so tired. But the members of Lava Expeditions provided me with lots of encouragement, which was one of the best memories. Finally we reached the top of Kilimanjaro in bright blue skies.

I felt excited about climbing Kilimanjaro and the feeling didn't change during my trip. Lava Expeditions looked after me so well that I was deeply thankful for their help.

    Stress is an inevitable part of a busy and modern life. Time and time again, we see people feeling overwhelmed because of stress. But after years of being dosed up by doctors and seeking solutions on the self-help shelves, can most common complaints be cured through your next holiday? The festival doctor will see you now.

    Complaint

    Prescription（处方）

    Dosage(剂量)

    Guilty

    Restart yourself at the Wanderlust Festival

    A weekend at any Wanderlust Festival should restrain some of the shame you are feeling. Empty your mind with meditation (冥想) sessions in the mountains of America or adjust your feelings with a sound bath in Santiago, Chile.

    Sad

    A healthy dose of laughter at Just for Laughs in Montreal, Canada in July.

Have fun at the largest comedy festival, which attracts more than two million ha-ha hunters every summer. Apart from 250 comedy acts, there will be walkabout theater ,circus acts and lots of new comedy films to make you laugh to tears.

    Over- thinking

    Get nourishing food for your thought at the U.K.'s How the Light Gets In in May.

    Spend a week or so in the company of like-minded individuals and you will see you are not the only one over-thinking things. The world's largest philosophy festival, held in Hareous Wye, will have talks, debates and classes on culture, philosophy, politics, art and science.

    Heart-broken

    Find one of your favorite fish in the sea at Ireland's Matchmaking Festival in June.

    A week at Liverpool's Matchmaking Festival could be a choice as Ireland's mythical matchmakers have been pairing lovers together for centuries. Try to find Willie Dally, a fourth-generation matchmaker, for your best chance of everlasting love. Those who touch his lucky book are said to fall in love and marry within six months.

    Dutch masters exhibition in Beijing

    The 17th century Dutch Golden Age had several significant artists and a range of great pieces produced during the period—including Jan Vermeer's Young Woman at Virginal,Jan Lievens' Boy in a Cape,and Turban and Rembrandt's Self-Portrait with Shaded Eyes.

    Some of the most refined examples of the time,including the three pieces mentioned above,will make their debut（首次亮相）in China as part of a world tour of The Leiden Collection.

    If you go:

    9 a.m.-5 p.m.,June 17-Sept 3 (closed on Mondays).National Museum of China,I Wusi Avenue,Dongcheng district.010-6400-1476.

    Ticket: 50 yuan ($7)

    The Age of Mechanical Reproduction

    The Age of Mechanical Reproduction,the latest exhibition at the Riverside Art Museum,features 41 artworks of US pop icon Andy Warhol,covering art installations,paintings and photographs.Warhol's well-known installation Electric Chair is a highlight of the show,which is also its debut in Asia.

    If you go:

    10 a.m.-5 p.m.,through August 28 (closed on Mondays).The Riverside Art Museum,Hongyan Road,Chaoyang district.010-5309-2062.

    Ticket: 60 yuan

    Back with a bang

    Beijing-based hand Escape Plan will hold a concert in Beijing this weekend.The band is most famous for the song The Brightest Star in the Night Sky.

    If you go:

    7:30 p.m.,June 17.Beijing Worker's Gymnasium,Gongti Beilu,Chaoyang district.400-610-3721.

    Ticket: 280-980 yuan

    Purple clay teapots

    Yixing purple clay potteries are a vital part of Chinese pottery culture and have been included in China's list of national intangible cultural heritage（国家非物质文化遗产）.A selection of more than 80 purple clay teapots will go on display at the Poly Art Museum starting Friday.The exhibit will include a range of delicate teapot works of Ji Yishun,Wang Xiaolong and Gao Lijun,who are all inheritors（继承人）the time-honored（历史悠久的）pottery handicraft.

    If you go:

    9:30 a.m.-4:30 p.m.(closed on Sundays),through June 30.Poly Art Museum,New Poly Plaza,1 Chaoyangmen North Street 9.010-6500-8117.

    Ticket: 20 yuan

    Being an astronaut sounds cool, doesn't it? In space, they get to do some pretty amazing things, like floating (漂浮) in zero gravity(重力).

    However, there are also plenty of things that astronauts can't do because of their weightless environment(环境), and that's very sad. What's worse, they can't even let their sadness show -because it's impossible to cry in zero gravity.

    Of course, astronauts can still produce tears. But crying is much more difficult in space, reported The Atlantic in January. Without gravity；tears don't flow downward out of the eyes like they do here on Earth. This means that when you cry in space, your tears have nowhere to go — they just stick to your eyes.

    In May 2011, astronaut Andrew Feustel experienced this during one of his spacewalks. "Tears," he said, "don't fall off your eye...They just kind of stay there."

    Besides making your vision(视觉) unclear, this can also cause physical pain. Back on Earth, tears are supposed to bring comfort to the eyes. But that's not the case in space. The space environment dries out astronauts' eyes, and when tears suddenly wet the eyes, it can cause pain rather than comfort. "My right eye is painful like crazy." Feustel told his teammate during the walk.

    Since gravity doesn't work in space, astronauts need some extra help to get rid of the tears. Feustel chose to rub his eyes against his helmet to wipe the tears away. Another choice is to just wait — "When the tears get big enough they simply break free of the eye and float around," astronaut Ron Parise told The Atlantic.

    There are lots of small things — things like crying — that we are so used to on Earth, we usually take them for granted, until they become a problem in a totally different environment, like space. There, astronauts can't talk to each other directly. They also can't eat or drink in normal ways. They can't even burp (打嗝), because there is no gravity to hold the food down in their stomach. If they do burp, they just end up throwing up (呕吐) everything in their stomach, according to the UK National Space Center.

    Thus, perhaps it's only space explorers who can honestly say, "Gravity, you're the best."

    More than two thirds of the world's polar bears will be wiped out by 2050, according to a shocking new study. By then, scientists say, global warming will have melted 42 percent of the Arctic sea ice. By 2100, only a very few of these important creatures will be left.

    The report has been produced by the US Geological Survey. The scientists have publicized their findings in the hope of influencing US Interior Secretary Dirk Kempthorne, who has been asked to put polar bears on the US endangered species list.

    Polar bears depend on floating sea ice as a platform for hunting seals, which are their main food. Without enough ice, polar bears would be forced to go onto the land, where they are poorly skilled hunters, and would be unlikely to adapt to the life on the land in time. Experts say few little bears would survive and the stress could make many females unable to get pregnant.

    The team of American and Canadian scientists spent six months studying bears, on the ground, from spotter planes and in the lab, using computer models. Some team members fear the result is even worse for the bears than what their report says. They say the Arctic is warming faster than anywhere in the world and much faster than their computer had been forecasting. Satellite observations have showed that the ice has decreased to an all­time low.

    However, not everyone in the scientific community believes that global warming is happening on such an alarming scale. Another investigation has found that polar bears are still being hunted by wealthy “sportsmen” who want their skins and heads. At least ten international companies offer bear­hunting trips.