Birdsknowwheretogowhenit’stimetomigrate.Theygetsomeofth...

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Birds know where to go when it’s time to migrate. They get some of that superb sense of direction from their ability to spot Earth’s magnetic field. That magnetic sense acts a bit like a compass used by human hikers. But the energy coming from some electronic devices can perturb a bird’s internal compass. And that might confuse a bird’s sense of direction.

Most electronic devices send out waves of energy called electromagnetic radiation. The levels are too low to harm people. Any given devices only sends out a small amount. But some types of this radiation could pose a problem to birds.

Even when held captive in a lab, birds know when it’s time to migrate. They are uneasy in their cages. They try to face in the direction they would fly away, if outdoors. But the birds can’t always line up correctly, notes Henrik Mouritsen.

Joseph Kirschvink has called for researchers to be more careful when studying the effects of electronic devices on bird’s sense of direction. He studies animals’ magnetic sense. He says Mouritsen’s team has done better work than any previous team in probing how electronic noise might affect birds’ magnetic compass. As a result of this study, he said, “I think it needs to be considered seriously.” He also said he hopes to see other scientists try to prove the new findings by running similar tests.

Mouristen’s experiments began back in 2004. He observed that caged robins did not face toward their migratory direction. For several years he could not figure out why. Then another researcher in his lab suggested that they set up a shield. Called a Faraday cage, it consisted of grounded aluminium screens that blocked incoming electromagnetic radiation. When protected by the screening, birds in the lab at last faced in the direction they should migrate.

Mouristen told he was reluctant to start studying birds and electromagnetic radiation. After all, he knew that previous experiments that tested its effects on animals had been criticized as funny. “It’s not the first time it’s been claimed,” he said of the link between compass confusion and electronics. “But I hope it’s the first time it has help up.”

27. The underlined word “perturb” in paragraph 1 probably means______.

A. bother B. protect C. check D. ruin

28. What puzzled Mouristen for years?

A. How birds can be protected from electromagnetic noise.

B. How electronic devices disturb a magnetic compass.

C. Why caged birds can’t face in the right direction

D. What are included in the biology of animals.

29. According to the last paragraph, Mouristen believe that _____.

A. the birds’ sense of direction did exist

B. the former experiments were really funny

C. birds’ compass confusion is linked with electronics

D. his team first claimed the link between compass confusion and electronics