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Climate change will force exhausted birds migrating to Europe from Africa to travel further, with possibly disastrous consequences, according to a study.

The annual voyage of some species, which fly north in search of food and suitable habitats, could increase by as much as 400 kilometers (250miles), the research found. “Marathon migrations for some birds are set to become even longer，” said Stephen Willis, a professor at Durham University in Britain and the main architect of the study. “This is bad news for birds like the Whitethroat, a common farmland bird. The added distance is a considerable threat. As temperatures rise and habitats change, birds will face their biggest challenge since the Pleistocene era (更新世：始于距今180萬年), which ended 11,000 years ago，” he said in a statement.

Some 500 million birds migrate each year from Africa, some weighing as little as nine grams (three－tenths of an ounce). To complete a voyage that can be thousands of kilometers long, birds have to fatten themselves up to twice their normal weight. Some even shrink their internal organs (收縮內(nèi)臟) to become more fuel efficient, so any additional distance may be dangerous.

The study finds that from 2071 to 2100, nine out of 17 species examined are going to face longer migrations, particularly birds that cross the Sahara Desert. Some birds traverse the Sahara and the Mediterranean Sea in a one go, while others have a break in northern Africa before crossing. Many fly at night, when temperatures are cooler.

A few—such as the Blackcap—have started to adapt by spending winters in Britain, but such behaviour remains exceptional, the study said. The study forecasts that the migration distance of the Orphean Warbler will jump from 2,700 kilometers (1,700 miles) to between 3,050 and 3,350 kilometers (1,900 and 2,100miles), with even longer increases for the Subalpine and Barred Warblers.

6. What does travelling extra distance mean for some migrating birds?

A. Better living conditions.       B. Better physical health.

C. Stronger ability to fly.         D. Bigger threat to life.

7. To complete the marathon migrations, some birds have to do the following except________.

A. have a break in Sahara  

B. put on more weight

C. reduce the size of internal organs

D. fly at night to avoid the heat

8. What does the underlined word “traverse”in the fourth paragraph mean?

A. Examine.            B. Face.         C. Cross.         D. Challenge.

9. What can we infer from the text?

A. Birds have to migrate from Africa to Europe in winter.

B. Global warming is bad for all birds worldwide.

C. Birds that are of small size don't need to migrate.

D. Some birds have to migrate unless they adapt to climate change.

10. What's the BEST title of the text?

A. Climate change leads to disastrous consequence

B. The annual voyage of some species

C. How birds migrate for longer distances

D. Climate change pushes birds to migrate farther