2009 进军美利坚作文组 wondersmiths2第二十一次作业 9.9

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高分 practice 9
In the lecture, the speaker talks about the theories about birds’ navigation. He strongly casts doubt on the arguments stated in the reading passage, due to the following reasons.

First, the theory that birds navigated by using the sun is doubted for the reason that birds still can fly at night without sun. Besides, the fact that only one bird specie has been found to navigate by using the star cannot be sufficient to prove that other species navigate in the same way. So, this is a direct contrast to the view displayed in the reading passage.

Second, birds maybe can remember the landmarks after first journey, but how can they navigate before the journey?
It still cannot explain why birds can navigate in strange places. Hence, the opinion in the reading passage is not convincing.

Finally, even if birds really navigate by sensing the earth's magnetic, they only can identify the north and south direction. How can they exactly orient themselves go to the destination? It is very difficult even for human. Therefore, this theory demonstrated in the reading passage is also doubtful.