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  3. You Call It Music, They Call It an Air Raid Songs can have a powerful effect on people. Play " Gypsies, Tramps and Thieves"

You Call It Music, They Call It an Air Raid Songs can have a powerful effect on people. Play " Gypsies, Tramps and Thieves"

admin2013-07-11  92
问题                     You Call It Music, They Call It an Air Raid
    Songs can have a powerful effect on people. Play " Gypsies, Tramps and Thieves" to many baby boomers, for example, and chances are they’ll run off, hands over their ears. Songs can have a powerful effect among birds, too. Consider the black-capped chickadee. When it sings its " chick-a-dee" song, its flock mates come running. The song is a warning that a hawk, owl or other predator is moving nearby, and the other chickadees arrive to harass the enemy until it leaves.
    Researchers from the University of Montana have discovered that this warning call is a coded signal. By varying the call, a bird communicates to other birds the size of the predator, and thus the scope of the danger. " This is so far the most finely detailed alarm call system that we’ve found," said the lead researcher, Christopher N. Templeton, who is now a doctoral student at the University of Washington. The findings appear in the current issue of the journal Science.
    Mr.Templeton and his colleagues exposed chickadees to 15 different species of predators and recorded and analyzed the calls the birds made. In addition to "chick-a-dee", the birds make a high-pitched "sect" call when they spy a predator flying in the air. Upon hearing this call, the other birds either dive for cover or remain motionless so as not to be spotted. But it’s the "chick-a-dee" call that the researchers focused on. "They change a number of different features about these calls," Mr. Templeton said. "But most are not audible to us except the number of dees’ at the end."
They found that the birds varied the number of "dee" sounds depending on the size of the predator. More "dees"—as many as 21 in one case—were sounded for smaller predators like the Northern pygmy owl. Because chickadees are small and fast, smaller, more quick-moving predators are more of a threat than larger ones.
    The more "dees", the more chickadees show up to harass the predator, by dive-bombing it or making noises in its face. "The goal is to drive it out of their territory so that it is no longer a threat," Mr. Templeton said. This "mobbing" response to the calls is probably learned behavior, he said, a way that birds teach their young about risks. "It’s a means by which adults tell the kids in the flock, ’ These guys are dangerous,’" Mr. Templeton said.
Which of the following is Not true about chickadees?
选项 A、Their songs not only warn but also communicate.
B、A smaller type of hawk is more dangerous than a larger one.
C、They mob the enemy by native instinct.
D、Their calls mostly cannot be heard by human being.
答案C
解析 本题考查事实细节。由第五段后半部分可知，它们共同对付敌人的反应是“后天学习”(learned behavior)的，所以[C]项与事实不符。第一段提到，鸟的歌声能警告捕食动物就在附近，第二段第二句又提到鸟的呼叫也可以传达关于捕食动物大小等的具体信息，因此[A]项内容正确。[B]项内容在第四段最后一句提到。[D]项内容在第三段的最后一句提到。
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